Journal: Proceedings of the National Academy of Sciences of the United States of America
Article Title: Otoferlin is a multivalent calcium-sensitive scaffold linking SNAREs and calcium channels
doi: 10.1073/pnas.1703240114
Figure Lengend Snippet: Otoferlin interacts with Loop1.3. (A, Upper) Representative SDS/PAGE showing results of immunoprecipitation of otoferlin from lysate of HEK293 cells cotransfected with YFP-otoferlin and mCherry-Loop1.3. Both otoferlin and Loop1.3 precipitate. (A, Lower) Representative SDS/PAGE showing results of immunoprecipitation of YFP from lysate of HEK293 cotransfected with YFP and mCherry-Loop1.3. YFP but not Loop1.3 precipitates. IP, immunoprecipitated pellet; total lysate, lysate before immunoprecipitation. (B) Quantitation of coimmunoprecipitation showing the fraction of each protein in the IP and supernatant (n = 3 biological replicates; error = SE). (C) Cartoon depicting smCoBRA. Titration of a fluorescently labeled ligand onto immobilized YFP-otoferlin results in colocalized fluorescent puncta. The resulting saturation curve is fitted to obtain a dissociation constant Kd. (D) Dose–response for YFP-otoferlin titrated with Loop1.3 at increasing concentrations (0.1–50 µM) of free calcium. Each data point represents the mean of three biological replicates (n = 3). Experimental data are fit with a Langmuir isotherm (solid lines). Inset depicts 0–10 µM for clarity. (E) Determined Mander’s colocalization coefficients M1 (black) and M2 (red) for a dose–response of Loop1.3 titrated onto YFP-otoferlin (0.1 µM calcium). Inset depicts 0–10 µM. (F) Dose–response for immobilized synaptotagmin I titrated with Loop1.3 in the presence of 0.1 or 30 μM calcium (n = 3). Colocalization between Loop1.3 and YFP-otoferlin is included for comparison. (G) Dose–response for immobilized synaptotagmin I titrated with the loop II–III region of Cav2.2 in in the presence of 0.1–50 μM calcium (n = 3). Inset depicts 0–10 µM for clarity. MCC, Mander's correlation coefficients.
Article Snippet: Similarly, mCherry-Loop1.3 was created by first subcloning mCherry plus a 30-nt 3′ linker, supplied by Addgene (plasmid 29722), into CKAR via HindIII and KpnI sites and then subsequently subcloning Loop1.3 amino acids 752–891 into the KpnI and XbaI sites via PCR.
Techniques: SDS Page, Immunoprecipitation, Quantitation Assay, Titration, Labeling, Comparison