Journal: The Journal of Biological Chemistry

Article Title: Rab5 nucleotide binding promotes oxidative metabolism to fuel hepatocellular carcinoma cell proliferation

doi: 10.1016/j.jbc.2026.111321

Figure Lengend Snippet: Rab5 is recruited to lipid droplets (LDs) in a GTPase-dependent manner in Hep3B cells . Super-resolution confocal micrographs of Hep3B human hepatoma cells expressing ( A ) WT Rab5 (GFP-Rab5 WT), ( B ) constitutively active mutant (GFP-Rab5 Q79L), and ( C ) dominant-negative mutant (GFP-Rab5 S34N). LDs were stained with Oil Red O (ORO, red ) to visualize neutral lipid stores. GFP-Rab5 fluorescence (green ) marks Rab5 localization. Inlays depict Rab5 localization around LD borders, indicated further by yellow arrows . D , quantification of Rab5–LD colocalization by the ratio of LD:cytoplasm GFP-Rab5 intensity. Graphs represent mean ± SD from n = 3 independent experiments. Statistical significance was determined using one-way ANOVA with Tukey’s post hoc test. ∗∗ p < 0.01 and ∗∗∗ p < 0.001.

Article Snippet: Formalin-fixed, paraffin-embedded sections were stained with an anti-Rab5 primary antibody (Cell Signaling Technology, 3547) followed by standard immunohistochemistry detection procedures.

Techniques: Expressing, Mutagenesis, Dominant Negative Mutation, Staining, Fluorescence

Journal: The Journal of Biological Chemistry

Article Title: Rab5 nucleotide binding promotes oxidative metabolism to fuel hepatocellular carcinoma cell proliferation

doi: 10.1016/j.jbc.2026.111321

Figure Lengend Snippet: Enhanced recruitment of Rab5 to lipid droplets (LDs) upon lipophagy stimulation . A , Western blot analysis of Rab5 and EEA1 GTP-pulldown in regular medium (CT) or 4 h HBSS starvation in Hep3B cells. B , quantification of the fold change of GTP-bound/total Rab5 as well as EEA1 from n = 4 independent experiments. C , quantification of total Rab5–β-actin confirming that starvation does not change overall Rab5 expression. D , Western blot analysis of LDs isolated from Hep3B cells by density gradient centrifugation showing abundant levels of Rab5 in isolated LDs following 4 h of HBSS starvation compared with the regular medium (CT). E , quantification of Rab5–Plin2 in the biochemically isolated LDs. F , fluorescence micrograph showing immunofluorescence staining of Hep3B cells expressing Myc-tagged Rab5 ( green ). Cells were treated with oleic acid for 16 h and then either maintained in regular medium (control) or subjected to 4 h of HBSS starvation before being fixed and stained with Oil Red O (ORO; red ) to label LDs. Note the marked increase in Rab5 staining around LDs in HBSS-starved cells versus control ( yellow arrowheads ). Graphs represent mean ± SD from n = 3 to 4 independent experiments. Statistical significance was determined using an unpaired two-tailed t test. ∗ p < 0.05, ∗∗ p < 0.01, and ∗∗∗ p < 0.001. CT, control; EEA1, early endosome antigen 1; HBSS, Hank’s balanced salt solution; Plin2, perilipin-2.

Article Snippet: Formalin-fixed, paraffin-embedded sections were stained with an anti-Rab5 primary antibody (Cell Signaling Technology, 3547) followed by standard immunohistochemistry detection procedures.

Techniques: Western Blot, Expressing, Isolation, Gradient Centrifugation, Fluorescence, Immunofluorescence, Staining, Control, Two Tailed Test

Journal: The Journal of Biological Chemistry

Article Title: Rab5 nucleotide binding promotes oxidative metabolism to fuel hepatocellular carcinoma cell proliferation

doi: 10.1016/j.jbc.2026.111321

Figure Lengend Snippet: Inhibition of Rab5 GTPase activity reduces lipid droplet (LD) catabolism via its GTPase activity . A , Western blot analysis of Rab5 and EEA1 GTP-pulldown in Hep3B cells treated with DMSO (CT) or NAP (100 μM, 48 h). B , quantification of GTP/total Rab5 as well as EEA1 from n = 3 independent experiments. C , confocal micrograph showing ORO-stained LDs ( red ) and DAPI-stained nuclei from Hep3B cells treated with DMSO (control) and NAP (100 μM). D , bar graphs depict quantification of LD number/cell, total LD area/cell, and LD size. E , confocal micrograph showing ORO-stained LDs (red ) and DAPI-stained nucleus from Hep3B cells treated with DMSO (control) and NAP (100 μM) with oleic acid (OA, 150 μM). F , bar graphs depict quantification of LD number/cell, total LD area/cell, and LD size. G , cartoon depicting NAP alteration of Rab5 GTP binding. Graphs represent mean ± SD from n = 3 independent experiments. Statistical significance was determined using an unpaired two-tailed t test. ∗ p < 0.05, ∗∗ p < 0.01, and ∗∗∗ p < 0.001. CT, control; DAPI, 4′,6-diamidino-2-phenylindole; DMSO, dimethyl sulfoxide; EEA1, early endosome antigen 1; NAP, neoandrographolide; ORO, Oil Red O.

Article Snippet: Formalin-fixed, paraffin-embedded sections were stained with an anti-Rab5 primary antibody (Cell Signaling Technology, 3547) followed by standard immunohistochemistry detection procedures.

Techniques: Inhibition, Activity Assay, Western Blot, Staining, Control, Binding Assay, Two Tailed Test

Journal: The Journal of Biological Chemistry

Article Title: Rab5 nucleotide binding promotes oxidative metabolism to fuel hepatocellular carcinoma cell proliferation

doi: 10.1016/j.jbc.2026.111321

Figure Lengend Snippet: Inhibition of Rab5 decreases HCC energy homeostasis . A , Seahorse metabolic analysis showing NAP (100 μM, 48 h) inhibition of Rab5 decreases oxygen consumption rate (OCR) compared with control in complete media. n = 3 independent experiments. B , quantification of basal and spare respiratory capacity in complete media following treatment with NAP. C , Seahorse metabolic analysis showing DMSO versus NAP treatment in Hep3B cells under 4 h HBSS starvation. D , quantification of basal and spare respiratory capacity from C . Graphs represent mean ± SD from n = 3 independent experiments. Statistical significance was determined using an unpaired two-tailed t test. ∗ p < 0.05, ∗∗ p < 0.01. DMSO, dimethyl sulfoxide; HBSS, Hank’s balanced salt solution; HCC, hepatocellular carcinoma; NAP, neoandrographolide.

Article Snippet: Formalin-fixed, paraffin-embedded sections were stained with an anti-Rab5 primary antibody (Cell Signaling Technology, 3547) followed by standard immunohistochemistry detection procedures.

Techniques: Inhibition, Control, Two Tailed Test

Journal: The Journal of Biological Chemistry

Article Title: Rab5 nucleotide binding promotes oxidative metabolism to fuel hepatocellular carcinoma cell proliferation

doi: 10.1016/j.jbc.2026.111321

Figure Lengend Snippet: Rab5 is upregulated in HCC and associated with cancer hallmarks . A , volcano plot from TNMplot showing expression of known lipid droplet (LD)–associated proteins, including Rab5A/B/C, in HCC tumors versus adjacent normal tissues from n = 53 patients. B , representative immunohistochemistry images from a liver tissue microarray showing Rab5 staining in normal liver (n = 4) versus HCC specimens (n = 7). C , quantification of Rab5 immunohistochemistry scores from the tissue microarray (mean ± SD, ∗∗∗ p < 0.0002; Welch's t test). D , cancer hallmark gene set enrichment analysis based on the study by Menyhart et al . , showing Rab5-associated genes enriched in proliferation, invasion, and evading growth suppressors. E , Kaplan–Meier survival analysis from the TCGA–LIHC dataset stratified by Rab5 expression. High Rab5 expression correlates with poorer overall survival (log-rank test, p = 0.06). HCC, hepatocellular carcinoma; LIHC, Liver Hepatocellular Carcinoma Cohort; TCGA, The Cancer Genome Atlas.

Article Snippet: Formalin-fixed, paraffin-embedded sections were stained with an anti-Rab5 primary antibody (Cell Signaling Technology, 3547) followed by standard immunohistochemistry detection procedures.

Techniques: Expressing, Immunohistochemistry, Microarray, Staining

Journal: The Journal of Biological Chemistry

Article Title: Rab5 nucleotide binding promotes oxidative metabolism to fuel hepatocellular carcinoma cell proliferation

doi: 10.1016/j.jbc.2026.111321

Figure Lengend Snippet: Working model depicting Rab5-mediated lipid droplet (LD) catabolism in HCC . Under nutrient deprivation, Rab5 GTP binding is increased and promotes a higher frequency of interaction with LDs, driving tethering and fusion with lysosomes via microlipophagy. Inside the lysosome, lysosomal acid lipase (LAL) degrades LD, releasing free fatty acids (FFAs), which are then shuttled to mitochondria for β-oxidation to fuel HCC cell proliferation and survival. HCC, hepatocellular carcinoma.

Article Snippet: Formalin-fixed, paraffin-embedded sections were stained with an anti-Rab5 primary antibody (Cell Signaling Technology, 3547) followed by standard immunohistochemistry detection procedures.

Techniques: Binding Assay

Journal: The Journal of Biological Chemistry

Article Title: Rab5 nucleotide binding promotes oxidative metabolism to fuel hepatocellular carcinoma cell proliferation

doi: 10.1016/j.jbc.2026.111321

Figure Lengend Snippet: Rab5 is recruited to lipid droplets (LDs) in a GTPase-dependent manner in Hep3B cells . Super-resolution confocal micrographs of Hep3B human hepatoma cells expressing ( A ) WT Rab5 (GFP-Rab5 WT), ( B ) constitutively active mutant (GFP-Rab5 Q79L), and ( C ) dominant-negative mutant (GFP-Rab5 S34N). LDs were stained with Oil Red O (ORO, red ) to visualize neutral lipid stores. GFP-Rab5 fluorescence (green ) marks Rab5 localization. Inlays depict Rab5 localization around LD borders, indicated further by yellow arrows . D , quantification of Rab5–LD colocalization by the ratio of LD:cytoplasm GFP-Rab5 intensity. Graphs represent mean ± SD from n = 3 independent experiments. Statistical significance was determined using one-way ANOVA with Tukey’s post hoc test. ∗∗ p < 0.01 and ∗∗∗ p < 0.001.

Article Snippet: The GFP-Rab5 was a gift from Marci Scidmore (Addgene plasmid #49888).

Techniques: Expressing, Mutagenesis, Dominant Negative Mutation, Staining, Fluorescence