Journal: bioRxiv

Article Title: Branched actin constrains endosomal cargo to control sorting and fission

doi: 10.64898/2026.03.10.710749

Figure Lengend Snippet: Inhibition of branched actin leads to increased endosome size. (A-J) . HeLa cells were ( A-C ) untreated, ( D-E ) treated with the formin inhibitor SMIFH2 (25 µM), ( F-G ) treated with the inactive control CK-689 (300 µM), or ( H-J ) the ARP2/3 branched actin inhibitor CK-666 (300 µM) for 50 min. Cells were fixed and stained with EEA1 and cortactin. Merged images (panels C and J ) show decreased cortactin at endosomes upon CK-666 treatment. (K) . Quantification of the effects of the inhibitors on endosome size as depicted in A-J. Imaris software was used to render EEA1-decorated endosomes as surfaces, and endosome size for each treatment (µm 2 ) was normalized to the average endosome size of the untreated group. Quantification represents 30 images from three independent experiments, including ∼50,000 endosomes per treatment. A two-tailed Mann-Whitney nonparametric test was used to determine p -values between treatment groups.

Article Snippet: HeLa cells (ATCC-CCL-2) were cultured with complete DMEM (high glucose) (ThermoFisher Scientific, Carlsbad, CA) containing 10% fetal bovine serum (FBS) (Sigma-Aldrich), 1× penicillin-streptomycin, 100 μg/mL Normicin, and 2 mM L-glutamine at 37°C in a humidified incubator with 5% CO2.

Techniques: Inhibition, Control, Staining, Software, Two Tailed Test, MANN-WHITNEY

Journal: bioRxiv

Article Title: Branched actin constrains endosomal cargo to control sorting and fission

doi: 10.64898/2026.03.10.710749

Figure Lengend Snippet: Transferrin recycling is impaired upon ARP2/3 inhibition. (A-D) . HeLa cells on coverslips were incubated with fluorophore-labeled transferrin (Tf-488) for 10 minutes of uptake. Cells were ( A ) untreated, ( B ) treated with 25 µM SMIFH2, ( C ) treated with 300 µM CK-689, or ( D ) treated with 300 µM CK-666 during the transferrin uptake. Images are representative of a treated coverslip after uptake. (E-H) . Cells were chased in ( E ) complete media, ( F ) complete media containing 25 µM SMIFH2, ( G ) complete media containing 300 µM CK-689, or ( H ) complete media containing 300 µM CK-666 for 40 minutes to allow recycling. Images are representative of cells on an treated coverslip after chase. (I) . The arithmetic mean intensity of each image was analyzed using Zeiss Zen Blue software after uptake and chase. For each treatment condition, the internalized mean for the uptake was set at 100%, and the arithmetic mean intensity for each recycling image was expressed as a percentage of the normalized uptake for that condition. Quantification represents 30 images from three independent experiments. Statistical significance was determined using a two-tailed unpaired t -test.

Article Snippet: HeLa cells (ATCC-CCL-2) were cultured with complete DMEM (high glucose) (ThermoFisher Scientific, Carlsbad, CA) containing 10% fetal bovine serum (FBS) (Sigma-Aldrich), 1× penicillin-streptomycin, 100 μg/mL Normicin, and 2 mM L-glutamine at 37°C in a humidified incubator with 5% CO2.

Techniques: Inhibition, Incubation, Labeling, Software, Two Tailed Test

Journal: bioRxiv

Article Title: Branched actin constrains endosomal cargo to control sorting and fission

doi: 10.64898/2026.03.10.710749

Figure Lengend Snippet: Transferrin and EGF are delayed at early endosomes upon ARP2/3 inhibition. (A-D) . HeLa cells were incubated with Tf-488 diluted in complete media for 10 min. Following uptake, cells were chased in ( A-B ) complete media or ( C-D ) in media containing 300 µM CK-666. Representative images are from the 30 min chase time point. (E). The percentage of Tf-488 fluorescence in EEA1 endosomes was calculated by measuring the area of Tf-EEA1 overlap as a percentage of total Tf fluorescence area. Statistical analysis was performed between the untreated and CK-666-treated groups at each time point. Quantification represents 24 images from three independent experiments. Statistical significance for the 30 min and 45 min time points was determined using a two-tailed Mann-Whitney nonparametric test, and an unpaired two-tailed t -test was used for the 15 min time point. (F). A bar graph showing the individual data points from the 30 min time point in ( E ). (G-J) . HeLa cells were serum starved for 1 h, then incubated with EGF-488 diluted in complete media for 10 min. Following uptake, cells were chased in ( G-H ) complete media or ( I-J ) in complete media containing 300 µM CK-666. Representative images are from the 45 min time point of media chase. (K). The percentage of EGF-488 fluorescence in EEA1-marked endosomes was calculated by measuring the area of EGF-EEA1 overlap as a percentage of total EGF fluorescence area. Statistical analysis was performed between the untreated and CK-666-treated groups at each time point. Quantification represents 24 images from three independent experiments. Statistical significance for the 15 min and 45 min time points was determined using a two-tailed Mann-Whitney nonparametric test, and an unpaired two-tailed t -test was used for the 30 min time point. (L). A bar graph showing the individual data points from the 45 min time point in ( K ).

Article Snippet: HeLa cells (ATCC-CCL-2) were cultured with complete DMEM (high glucose) (ThermoFisher Scientific, Carlsbad, CA) containing 10% fetal bovine serum (FBS) (Sigma-Aldrich), 1× penicillin-streptomycin, 100 μg/mL Normicin, and 2 mM L-glutamine at 37°C in a humidified incubator with 5% CO2.

Techniques: Inhibition, Incubation, Fluorescence, Two Tailed Test, MANN-WHITNEY

Journal: bioRxiv

Article Title: Branched actin constrains endosomal cargo to control sorting and fission

doi: 10.64898/2026.03.10.710749

Figure Lengend Snippet: Branched actin inhibition, but not formin inhibition, decreases actin at RAB5 QL endosomes. (A-P) . HeLa cells were transfected with mCherry-RAB5 Q79L and were either ( A-D ) untreated or treated with ( E-H ) 25 µM SMIFH2, ( I-L ) 300 µM CK-689, or ( M-P ) 300 µM CK-666 for 20 min. Cells were fixed and co-stained with cortactin and phalloidin to visualize the actin network. (Q) . Quantification of ( A-P ). RAB5 Q79L endosomes that colocalized with phalloidin or cortactin were counted as a percentage of total RAB5 Q79L endosomes. Quantification represents 15 images from three independent experiments. A two-tailed Mann-Whitney nonparametric test was used to determine significance between treatment groups. Data comparisons without error bars are not significant ( p > 0.05).

Article Snippet: HeLa cells (ATCC-CCL-2) were cultured with complete DMEM (high glucose) (ThermoFisher Scientific, Carlsbad, CA) containing 10% fetal bovine serum (FBS) (Sigma-Aldrich), 1× penicillin-streptomycin, 100 μg/mL Normicin, and 2 mM L-glutamine at 37°C in a humidified incubator with 5% CO2.

Techniques: Inhibition, Transfection, Staining, Two Tailed Test, MANN-WHITNEY

Journal: bioRxiv

Article Title: Branched actin constrains endosomal cargo to control sorting and fission

doi: 10.64898/2026.03.10.710749

Figure Lengend Snippet: Transferrin is bounded by cortactin at endosomes. (A-L) . HeLa cells were transfected with mCherry-RAB5 Q79L and were incubated with ( A-C ) no inhibitor, ( D-F ) 25 µM SMIFH2, ( G-I ) 300 µM CK-689, or ( J-L ) 300 µM CK-666 for 4 min. Following the pre-treatment, cells were incubated with Tf-488 (and their respective inhibitor) for 6 min of uptake. (M-P) . Representative fluorescence intensity profiles of endosomes from ( M ) untreated, ( N ) SMIFH2-treated cells, ( O ) CK-689-treated cells, or ( P ) CK-666-treated cells. The intensity profile of Tf is in green, and the intensity profile of cortactin is in magenta. Tf vertices above 130% that occur within 20 degrees of a cortactin value above 130% are represented with a red circle; these peaks are “bounded”. Tf vertices above 130% that are not within 20 degrees of a cortactin value above 130% are represented with a grey circle and are “not bounded”. (Q). The percentage of “bounded” Tf peaks was quantified from fluorescence intensity profiles (as represented in ( M-P )). Quantification is from three independent experiments, and from 37 endosomes for the untreated group, 43 endosomes for SMIFH2-treated, 38 endosomes for CK-689-treated, and 37 endosomes from the CK-666-treated group. Statistical significance was determined using a two-tailed unpaired t -test (ns: p > 0.05). (R, S) . Representative models for the quantification and results of the experiment. A circle was drawn around the endosome membrane (red) that intersects with the regions of Tf (green) and cortactin (magenta), and fluorescence intensity at each degree around the circle was measured. ( R ) Untreated cells have Tf in confined regions on the endosome and are adjacent to regions of cortactin ∼60% of the time. ( S ) CK-666-treated cells have regions of Tf that are broader and “not bounded” by cortactin.

Article Snippet: HeLa cells (ATCC-CCL-2) were cultured with complete DMEM (high glucose) (ThermoFisher Scientific, Carlsbad, CA) containing 10% fetal bovine serum (FBS) (Sigma-Aldrich), 1× penicillin-streptomycin, 100 μg/mL Normicin, and 2 mM L-glutamine at 37°C in a humidified incubator with 5% CO2.

Techniques: Transfection, Incubation, Fluorescence, Two Tailed Test, Membrane

Journal: bioRxiv

Article Title: Branched actin constrains endosomal cargo to control sorting and fission

doi: 10.64898/2026.03.10.710749

Figure Lengend Snippet: Tf occupies less discrete regions on the endosome when branched actin is inhibited. (A-L) . HeLa cells were transfected with mCherry-RAB5 Q79L and were incubated with ( A-C ) no inhibitor, ( D-F ) 25 µM SMIFH2, ( G-I ) 300 µM CK-689, or ( J-L ) 300 µM CK-666 for 4 min. Following the pre-treatment, cells were incubated with Tf-488 (and their respective inhibitor) for 6 min of uptake. Untreated, SMIFH2-treated, and CK-689-treated cells show Tf localized to discrete regions on the endosome (yellow arrows). CK-666-treated cells have broader regions of Tf on the endosome (blue arrows). (M). Model for quantification. A circle (blue) was drawn around the endosome membrane (red) that intersects with the regions of Tf, and the fluorescence intensity at each degree around the circle was measured. (N-Q) . Representative fluorescence intensity profiles of Tf on the endosome from ( N ) untreated, ( O ) SMIFH2-treated, ( P ) CK-689-treated, and ( Q ) CK-666-treated cells. The profiles depicted are from the endosomes indicated with a magenta-colored star ( A-L ). (R). Tf-containing regions from the fluorescence intensity profiles ( N-Q ) were identified, and the fluorescence values ± 20 degrees from the maximum were normalized. These normalized profiles of Tf-containing regions are Tf “peaks”. The graph shows the average profile of 72 Tf peaks from 37 endosomes for the control group, 70 peaks from 43 endosomes from SMIFH2-treated cells, 73 peaks from 38 endosomes from CK-689-treated cells, and 70 peaks from 37 endosomes from CK-666-treated cells. Data are from three independent experiments. The average profile of Tf peaks in the CK-666-treated cells is broader (less discrete) than the other treatment groups. See table in Figure EV3 for statistical information.

Article Snippet: HeLa cells (ATCC-CCL-2) were cultured with complete DMEM (high glucose) (ThermoFisher Scientific, Carlsbad, CA) containing 10% fetal bovine serum (FBS) (Sigma-Aldrich), 1× penicillin-streptomycin, 100 μg/mL Normicin, and 2 mM L-glutamine at 37°C in a humidified incubator with 5% CO2.

Techniques: Transfection, Incubation, Membrane, Fluorescence, Control

Journal: bioRxiv

Article Title: Branched actin constrains endosomal cargo to control sorting and fission

doi: 10.64898/2026.03.10.710749

Figure Lengend Snippet: EGF segregation on the endosome is affected by branched actin inhibition. (A-L) . HeLa cells were transfected with mCherry-RAB5 Q79L and were incubated with ( A-C ) no inhibitor, ( D-F ) SMIFH2, ( G-I ) CK-689, or ( J-L ) CK-666 for 4 min. Following the pre-treatment, cells were incubated with EGF-488 (and the respective inhibitor) for 17 min of uptake. Untreated, SMIFH2-treated, and CK-689-treated cells show EGF localized to discrete regions on the endosome (yellow arrows). CK-666-treated cells have broader regions of EGF on the endosome (blue arrows). (M-P) . Representative fluorescence intensity profiles of EGF on the endosome from the ( M ) untreated, ( N ) SMIFH2-treated, ( O ) CK-689-treated, and ( P ) CK-666 treated cells. The profiles depicted are from the endosomes indicated with a magenta star in ( A-L ). (Q) . EGF-containing regions from the fluorescence intensity profiles ( M-P ) were identified, and the fluorescence values ± 20 degrees from the maximum were normalized. These normalized profiles of EGF-containing regions are EGF “peaks”. The graph shows the average profile of 84 EGF peaks from 47 endosomes that were analyzed for the control group, 86 peaks from 51 endosomes from SMIFH2-treated cells, 72 peaks from 39 endosomes from CK-689-treated cells, and 86 peaks from 49 endosomes from CK-666-treated cells. Data are from three independent experiments. The average profile of EGF peaks in the CK-666-treated cells is broader (less discrete) than the other treatment groups. See table in Figure EV4 for statistical information.

Article Snippet: HeLa cells (ATCC-CCL-2) were cultured with complete DMEM (high glucose) (ThermoFisher Scientific, Carlsbad, CA) containing 10% fetal bovine serum (FBS) (Sigma-Aldrich), 1× penicillin-streptomycin, 100 μg/mL Normicin, and 2 mM L-glutamine at 37°C in a humidified incubator with 5% CO2.

Techniques: Inhibition, Transfection, Incubation, Fluorescence, Control

Journal: bioRxiv

Article Title: Branched actin constrains endosomal cargo to control sorting and fission

doi: 10.64898/2026.03.10.710749

Figure Lengend Snippet: The degradative and retrieval subdomains on endosomes coalesce upon branched actin inhibition. (A-F) . HeLa cells were transfected with mCherry-RAB5 Q79L and were co-incubated with EGF-488 and anti-CD59 antibody for 20 min. During the last 5 min of uptake, either ( A-C ) no inhibitor or ( D-F ) 300 µM CK-666 was added to the media. Pearson’s and Manders’ correlation coefficients for each representative image are listed. (G). ImageJ was used to calculate Pearson’s correlation coefficient for 47 ROIs in the untreated group and 42 ROIs in the CK-666-treated group from three independent experiments. Statistical significance was determined using an unpaired two-tailed t -test. (H, I) . ImageJ was used to calculate Manders’ correlation coefficients (M1 and M2) for 47 ROIs in the untreated group and 42 ROIs in the CK-666-treated group from three independent experiments. Statistical significance was determined using an unpaired two-tailed t -test.

Article Snippet: HeLa cells (ATCC-CCL-2) were cultured with complete DMEM (high glucose) (ThermoFisher Scientific, Carlsbad, CA) containing 10% fetal bovine serum (FBS) (Sigma-Aldrich), 1× penicillin-streptomycin, 100 μg/mL Normicin, and 2 mM L-glutamine at 37°C in a humidified incubator with 5% CO2.

Techniques: Inhibition, Transfection, Incubation, Two Tailed Test

Journal: The Journal of Cell Biology

Article Title: Small GTPase ActIvitY ANalyzing (SAIYAN) system: A method to detect GTPase activation in living cells

doi: 10.1083/jcb.202403179

Figure Lengend Snippet: Sar1 membrane association is efficiently detected using the Split mNeonGreen system. (A) Schematic representation of the SAIYAN system. The membrane-spanning regions of TANGO1S and HA-tag fused to 10 of the 11 strands of mNG (mNG 1–10 ) were expressed in cells. In addition, Sar1A constructs with a FLAG-tag and a glycine linker fused to the 11th strand of mNG (mNG 11 ) were also expressed. Upon Sar1A activation, mNG 1–10 and mNG 11 combined to form the complete mNG proteins, inducing mNG signals. (B) HA-mNG 1–10 cells transfected with the indicated Sar1A constructs were fixed and stained with anti-Sec16-C and anti-FLAG antibodies. Scale bar = 10 µm. (C) Quantification of mNG intensity from B (arbitrary units [A.U.]). Error bars represent the means ± SEM. Each data point represents the mNG intensity of the analyzed cells.

Article Snippet: Sar1A/SAIYAN (HeLa) cells on a 3.5-cm glass bottom dish (Matsunami) treated with or without doxycycline were transfected with Str-KDEL_ManII-SBP-mCherry (Addgene).

Techniques: Membrane, Construct, FLAG-tag, Activation Assay, Transfection, Staining

Journal: The Journal of Cell Biology

Article Title: Small GTPase ActIvitY ANalyzing (SAIYAN) system: A method to detect GTPase activation in living cells

doi: 10.1083/jcb.202403179

Figure Lengend Snippet: Validation of SAIYAN technology. (A) Doxycycline-inducible HeLa cells expressing the membrane-spanning region of TANGO1S and HA-tag fused to 10 of the 11 strands of mNG (HA-mNG 1–10 cells) were either non-transfected or transfected with Sar1A constructs with a FLAG tag and a glycine linker fused to the 11th strand of mNG (Sar1A-FLAG-mNG 11 ). The cells were fixed and stained with anti-HA and anti-PDI antibodies. Scale bar = 10 µm. (B) HA-mNG 1–10 cells, treated with or without doxycycline, were transfected with Sar1A-FLAG-mNG 11 . The cells were fixed and stained with anti-HA and anti-FLAG antibodies. Scale bar = 10 µm.

Article Snippet: Sar1A/SAIYAN (HeLa) cells on a 3.5-cm glass bottom dish (Matsunami) treated with or without doxycycline were transfected with Str-KDEL_ManII-SBP-mCherry (Addgene).

Techniques: Expressing, Membrane, Transfection, Construct, FLAG-tag, Staining

Journal: The Journal of Cell Biology

Article Title: Small GTPase ActIvitY ANalyzing (SAIYAN) system: A method to detect GTPase activation in living cells

doi: 10.1083/jcb.202403179

Figure Lengend Snippet: Production of Sar1A/SAIYAN cells. (A) Doxycycline-inducible stable cell lines expressing the membrane-spanning regions of TANGO1S and HA-tag fused to 10 of the 11 strands of mNG were established using a lentiviral system and G418 selection (HA-mNG 1–10 cells). Stable cells were subsequently electroporated with Cas9 protein, sgRNA, and ssDNA to facilitate the knock-in of FLAG-mNG 11 into the Sar1A locus of the genome. Cells were treated with doxycycline for 24 h and further sorted via FACS to isolate single cells exhibiting mNG signals into 96-well plates. The expanded cell population was then collected and subjected to genomic sequencing. Positive clones were identified and selected for further analysis (Sar1A/SAIYAN cells). (B) Sar1A/SAIYAN (HeLa) cells, either treated or non-treated with doxycycline, were fixed and stained with anti-HA and anti-PDI antibodies. Boxed areas in the middle panels are shown at high magnification in the bottom panels. Scale bars: 10 µm (main), 5 µm (magnification). (C) Sar1A/SAIYAN (HeLa) cells, either treated or non-treated with doxycycline, were fixed and stained with anti-HA and anti-FLAG antibodies. Boxed areas in the middle panels are shown at high magnification in the bottom panels. Scale bar:10 µm (main), 5 μm (magnification). (D) Sar1A/SAIYAN (HeLa) cells transfected with the indicated siRNAs were fixed and stained with an anti-Sec16-C antibody. Scale bar = 10 µm. (E) Quantification of mNG intensity from D (arbitrary units [A.U.]). Error bars represent the means ± SEM. Each data point represents the mNG intensity of the analyzed cells. (F) Sar1A/SAIYAN (HeLa) cells transfected with the indicated siRNAs were lysed and subjected to SDS-PAGE, followed by western blotting with anti-FLAG, anti-HA, anti-Sar1A, and anti-GAPDH antibodies. (G) Sar1A/SAIYAN (HeLa) cells, either treated or non-treated with doxycycline, were fractionated via centrifugation. The lysates, the supernatants, and the pellets were subjected to SDS-PAGE, followed by western blotting with anti-FLAG, Sar1A, HA, ERK1, and calnexin antibodies. Source data are available for this figure: .

Article Snippet: Sar1A/SAIYAN (HeLa) cells on a 3.5-cm glass bottom dish (Matsunami) treated with or without doxycycline were transfected with Str-KDEL_ManII-SBP-mCherry (Addgene).

Techniques: Stable Transfection, Expressing, Membrane, Selection, Knock-In, Genomic Sequencing, Clone Assay, Staining, Transfection, SDS Page, Western Blot, Centrifugation

Journal: The Journal of Cell Biology

Article Title: Small GTPase ActIvitY ANalyzing (SAIYAN) system: A method to detect GTPase activation in living cells

doi: 10.1083/jcb.202403179

Figure Lengend Snippet: Sar1A/SAIYAN (HeLa) cells proliferate and secrete normally. (A) HeLa and Sar1A/SAIYAN (HeLa) cells were treated with or without doxycycline for 24 h, and cell viability was measured and normalized using untreated HeLa cells as control. Error bars represent the means ± SEM. n = 4. (B) Sar1A/SAIYAN (HeLa) cells, treated with or without doxycycline, were fixed and stained with anti-Sec16-C and anti-GM130 antibodies. Scale bars = 10 µm. (C) Sar1A/SAIYAN (HeLa) cells treated with or without doxycycline were transfected with Str-KDEL_ManII-SBP-mCherry. RUSH chase was started with biotin addition, and live imaging was performed. Scale bars = 10 μm.

Article Snippet: Sar1A/SAIYAN (HeLa) cells on a 3.5-cm glass bottom dish (Matsunami) treated with or without doxycycline were transfected with Str-KDEL_ManII-SBP-mCherry (Addgene).

Techniques: Control, Staining, Transfection, Imaging

Journal: The Journal of Cell Biology

Article Title: Small GTPase ActIvitY ANalyzing (SAIYAN) system: A method to detect GTPase activation in living cells

doi: 10.1083/jcb.202403179

Figure Lengend Snippet: ER exit site organization is required for the efficient activation of Sar1A. (A, C, E, and G) Sar1A/SAIYAN (HeLa) cells transfected with the indicated siRNAs were fixed and stained with anti-Sec16-C antibodies. Scale bar = 10 µm. (B, D, F, and H) Quantification of mNG signals from A, C, E, and G, respectively (arbitrary units [A.U.]). Error bars represent the means ± SEM. Each data point represents the mNG intensity of the analyzed cells.

Article Snippet: Sar1A/SAIYAN (HeLa) cells on a 3.5-cm glass bottom dish (Matsunami) treated with or without doxycycline were transfected with Str-KDEL_ManII-SBP-mCherry (Addgene).

Techniques: Activation Assay, Transfection, Staining

Journal: The Journal of Cell Biology

Article Title: Small GTPase ActIvitY ANalyzing (SAIYAN) system: A method to detect GTPase activation in living cells

doi: 10.1083/jcb.202403179

Figure Lengend Snippet: Western blotting analysis of Sar1A/SAIYAN (HeLa) cells on , , and . (A) Sar1A/SAIYAN (HeLa) cells transfected with the indicated siRNAs were lysed and subjected to SDS-PAGE, followed by western blotting with anti-FLAG, anti-HA, anti-Sec12, and anti-GAPDH antibodies. (B) Sar1A/SAIYAN (HeLa) cells transfected with the indicated siRNAs were lysed and subjected to SDS-PAGE, followed by western blotting with anti-FLAG, anti-HA, anti-cTAGE5 CC1, anti-Sec12, and anti-GAPDH antibodies. (C) Sar1A/SAIYAN (HeLa) cells transfected with the indicated siRNAs were lysed and subjected to SDS-PAGE, followed by western blotting with anti-FLAG, anti-HA, anti-TANGO1 CC1, and anti-GAPDH antibodies. (D) Sar1A/SAIYAN (HeLa) cells transfected with the indicated siRNAs were lysed and subjected to SDS-PAGE, followed by western blotting with anti-FLAG, anti-HA, anti-Sec16-N, and anti-GAPDH antibodies. (E) Sar1A/SAIYAN (HeLa) cells transfected with the indicated siRNAs were lysed and subjected to SDS-PAGE, followed by western blotting with anti-FLAG, anti-HA, anti-Sec23A (11D8), and anti-GAPDH antibodies. (F) Sar1A/SAIYAN (HeLa) cells transfected with the indicated siRNAs were lysed and subjected to SDS-PAGE, followed by western blotting with anti-FLAG, anti-HA, anti-Sec31A (rabbit), and anti-GAPDH antibodies. (G) Sar1A/SAIYAN (HeLa) cells were stably expressed using mCherry-tagged Sec23A constructs as indicated. Cells were lysed and subjected to SDS-PAGE, followed by western blotting with anti-FLAG, anti-HA, anti-Sec23A (11D8), anti-Sec31A (rabbit), and anti-GAPDH antibodies. Source data are available for this figure: .

Article Snippet: Sar1A/SAIYAN (HeLa) cells on a 3.5-cm glass bottom dish (Matsunami) treated with or without doxycycline were transfected with Str-KDEL_ManII-SBP-mCherry (Addgene).

Techniques: Western Blot, Transfection, SDS Page, Stable Transfection, Construct

Journal: The Journal of Cell Biology

Article Title: Small GTPase ActIvitY ANalyzing (SAIYAN) system: A method to detect GTPase activation in living cells

doi: 10.1083/jcb.202403179

Figure Lengend Snippet: Sec23A and Sec31A depletion exerts opposite effects on the activation of Sar1A in living cells. (A and C) Sar1A/SAIYAN (HeLa) cells transfected with the indicated siRNAs were fixed and stained with anti-Sec16-C antibodies. Scale bar = 10 µm. (B and D) Quantification of mNG signals from A and C, respectively (arbitrary units [A.U.]). Error bars represent the means ± SEM. Each data point represents the mNG intensity of the analyzed cells. (E) Sar1A/SAIYAN (HeLa) cells transfected with the indicated plasmids were fixed and processed for microscopic analysis. Scale bar = 10 µm. (F) Quantification of mNG signals from E (A.U.). Error bars represent the means ± SEM. Each data point represents the mNG intensity of the analyzed cells.

Article Snippet: Sar1A/SAIYAN (HeLa) cells on a 3.5-cm glass bottom dish (Matsunami) treated with or without doxycycline were transfected with Str-KDEL_ManII-SBP-mCherry (Addgene).

Techniques: Activation Assay, Transfection, Staining

Journal: The Journal of Cell Biology

Article Title: Small GTPase ActIvitY ANalyzing (SAIYAN) system: A method to detect GTPase activation in living cells

doi: 10.1083/jcb.202403179

Figure Lengend Snippet: Each CLSD mutant of Sec23A exhibits different properties on Sar1 activation. (A) Sar1A/SAIYAN (HeLa) cells stably expressing mCherry-tagged Sec23A constructs, as indicated, were fixed and processed for microscopic analysis. Scale bar = 10 µm. (B) Quantification of mNG signals from A (A.U.). Error bars represent the means ± SEM. Each data point represents the mNG intensity of the analyzed cells.

Article Snippet: Sar1A/SAIYAN (HeLa) cells on a 3.5-cm glass bottom dish (Matsunami) treated with or without doxycycline were transfected with Str-KDEL_ManII-SBP-mCherry (Addgene).

Techniques: Mutagenesis, Activation Assay, Stable Transfection, Expressing, Construct

Journal: The Journal of Cell Biology

Article Title: Small GTPase ActIvitY ANalyzing (SAIYAN) system: A method to detect GTPase activation in living cells

doi: 10.1083/jcb.202403179

Figure Lengend Snippet: DPD treatment accumulates collagen I within the ER of Sar1A/SAIYAN (BJ-5ta) cells. Sar1A/SAIYAN (BJ-5ta) cells were treated with DMSO or 0.5 mM DPD and incubated for 16 h. Cells were fixed and stained with an anti-collagen I antibody. Scale bar = 10 µm.

Article Snippet: Sar1A/SAIYAN (HeLa) cells on a 3.5-cm glass bottom dish (Matsunami) treated with or without doxycycline were transfected with Str-KDEL_ManII-SBP-mCherry (Addgene).

Techniques: Incubation, Staining

Journal: The Journal of Cell Biology

Article Title: Small GTPase ActIvitY ANalyzing (SAIYAN) system: A method to detect GTPase activation in living cells

doi: 10.1083/jcb.202403179

Figure Lengend Snippet: Activated Sar1 prevails in the ERGIC region of Sar1A/SAIYAN (BJ-5ta) cells. (A–O) Sar1A/SAIYAN (BJ-5ta) cells were fixed and stained with anti-Sec16-C (A), anti-ERGIC53 (B), anti-Sec23 (5H2) (C), anti-Sec24B (D), anti-Sec24D (E), anti-p125A (F), anti-TANGO1-CT (G), anti-Sec12 (H), anti-TFG (I), anti-Sec13 (J), anti-Sec31A (mouse) (K), anti-β-COP (L), anti-GM130 (M), anti-PDI (N), and anti-Rab1A (O) antibodies. Images were captured using Airyscan2. Scale bars: 10 µm (main), 1 µm (magnification). (A–L) Right; top: Magnification of the indicated regions is on the left. Right; bottom: Magnification of the indicated regions on the upper. (P) Pearson’s correlation coefficient was used to quantify the degree of colocalization. n = 5. Cyan; outer COPII coats, blue; inner COPII coats, purple; ER exit site resident proteins, red; ERGIC proteins, orange; COPI protein, magenta; ER and Golgi proteins. Error bars represent the mean 95% CI.

Article Snippet: Sar1A/SAIYAN (HeLa) cells on a 3.5-cm glass bottom dish (Matsunami) treated with or without doxycycline were transfected with Str-KDEL_ManII-SBP-mCherry (Addgene).

Techniques: Staining

Journal: The Journal of Cell Biology

Article Title: Small GTPase ActIvitY ANalyzing (SAIYAN) system: A method to detect GTPase activation in living cells

doi: 10.1083/jcb.202403179

Figure Lengend Snippet: Triple staining of Sar1A/SAIYAN (BJ-5ta) and parental BJ-5ta reveals the organization of the ER-Golgi interface of collagen-secreting cells. (A–C) Sar1A/SAIYAN (BJ-5ta) cells were fixed and stained with anti-Sec16-C and anti-ERGIC53 (A), anti-Sec23 (5H2), and anti-ERGIC53 (B), and anti-Rab1A and anti-ERGIC53 (C) antibodies. Images were captured using the Airyscan2. Scale bars: 10 µm (main), 1 µm (magnification). (D) BJ-5ta cells were fixed and stained with anti-Sec16-C, anti-Sec23 (5H2), and anti-ERGIC53 antibodies. Images were captured using the Airyscan2. Scale bars: 10 µm (main), 1 µm (magnification). (A–D) (right; top) Magnification of the indicated regions is on the left. (right; bottom) Double staining of the magnified region on the top.

Article Snippet: Sar1A/SAIYAN (HeLa) cells on a 3.5-cm glass bottom dish (Matsunami) treated with or without doxycycline were transfected with Str-KDEL_ManII-SBP-mCherry (Addgene).

Techniques: Staining, Double Staining

Journal: The Journal of Cell Biology

Article Title: Small GTPase ActIvitY ANalyzing (SAIYAN) system: A method to detect GTPase activation in living cells

doi: 10.1083/jcb.202403179

Figure Lengend Snippet: Quantification of Pearson’s correlation coefficient to quantify the degree of colocalization in Sar1A/SAIYAN (HeLa) cells. Sar1A/SAIYAN (HeLa) cells were fixed and stained with anti-Sec16-C, anti-ERGIC53, anti-Sec23, anti-Sec24B, anti-Sec24D, anti-p125A, anti-TANGO1-CT, anti-Sec12, anti-TFG, anti-Sec13, anti-Sec31A (mouse), anti-β-COP, anti-GM130, anti-PDI, and anti-Rab1A antibodies. Images were captured using the Airyscan2. n = 5. Cyan; outer COPII coats, blue; inner COPII coats, purple; endoplasmic reticulum (ER) exit site resident proteins, red; ERGIC proteins, orange; COPI protein, magenta; ER and Golgi proteins. Error bars represent the mean 95% CI.

Article Snippet: Sar1A/SAIYAN (HeLa) cells on a 3.5-cm glass bottom dish (Matsunami) treated with or without doxycycline were transfected with Str-KDEL_ManII-SBP-mCherry (Addgene).

Techniques: Staining

Journal: The Journal of Cell Biology

Article Title: Small GTPase ActIvitY ANalyzing (SAIYAN) system: A method to detect GTPase activation in living cells

doi: 10.1083/jcb.202403179

Figure Lengend Snippet: Reticular pattern of activated Sar1 signals diminished with DPD treatment in Sar1A/SAIYAN (BJ-5ta) cells. (A) Sar1A/SAIYAN (BJ-5ta) cells were treated with DMSO or 0.5 mM DPD and incubated for 16 h. Cells were fixed and stained with anti-Sec16-C antibodies. Images were captured using the Airyscan2. Scale bars: 10 µm (main), 1 µm (magnification). (B) Pearson’s correlation coefficient was quantified to assess the degree of colocalization. n = 5. Error bars represent the mean 95% CI.

Article Snippet: Sar1A/SAIYAN (HeLa) cells on a 3.5-cm glass bottom dish (Matsunami) treated with or without doxycycline were transfected with Str-KDEL_ManII-SBP-mCherry (Addgene).

Techniques: Incubation, Staining