Journal: bioRxiv
Article Title: Novel signaling hub of insulin receptor, dystrophin glycoprotein complex and plakoglobin regulates muscle size
doi: 10.1101/517789
Figure Lengend Snippet: Affinity-based purification of plakoglobin-containing multiprotein assembly. A plasmid encoding 6His-tagged plakoglobin was electroporated into mouse TA mus cle, and 6His-plakoglobin-bound proteins were isolated with Nickel beads and identified by mass spectrometry. His-plakoglobin-bound proteins were eluted from Nickel column in (a) with a Histidine gradient (50-250 mM) and analyzed by immunoblotting. Elution fraction #2 was subjected to mass spectrometry (one experiment was performed and data compared to the experiment presented in ). Analysis of high MW protein peak fractions eluted from size exclusion chromatography (as in ) by SDS-PAGE and immunoblotting. n= two independent experiments. Plakoglobin was immunoprecipitated from the high MW protein peak, and bound proteins were detected by immunoblotting. Plakoglobin, DGC components (including glycosylated-β-dystroglycan), the insulin receptor, caveolin-1, desmin, and MuSK sediment to the same glycerol gradient fractions (marked bya red rectangle). Membrane-cytoskeleton fraction from mouse muscle was separated on 10-40% glycerol gradient, and alternate protein eluates were analyzed by Western blotting. n= two independent experiments. In normal muscle, plakoglobin, DGC components, the insulin receptor, and desmin interact. Left: proteins co-purified with anti-plakoglobin from glycerol gradient fraction #16 illustrated in (e) , and detected by immunoblotting. MuSK did not bind plakoglobin although it sedimented to the same fractions in (e). Right: a reciprocal immunoprecipitation with a-1-syntrophin antibody from membrane fractions isolated from normal TA muscle. Two experiments were performed: one with plakoglobin antibody and one with a-1-syntrophin antibody. Plakoglobin, β-dystroglycan, and the insulin receptor colocalize at costameres on skeletal muscle membrane. Confocal and STED images of TA muscle cross sections stained with the indicated antibodies. Scale bars, 5 µm (Confocal) and 2 µm (STED). n= three independent experiments indicating colocalization of these proteins. STED analysis is an annotated image in which all three proteins are detected using the spots module of lmaris software (white, red and green spheres). The double and triple co-occurrence spots are presented in yellow and blue, correspondingly. Proximity ligation assay (PLA) was performed on TA cross sections with β-dystroglycan and insulin receptor antibodies or β-dystroglycan antibody alone. Red fluorescent dots indicate areas of β-dystroglycan-insulin receptor association.
Article Snippet: Moreover, a built-in Imaris plugin spot colocalization algorithm (requiring ImarisXT module) was used to identify triple spots centers with maximum distance of 250nm.
Techniques: Affinity Purification, Plasmid Preparation, Isolation, Mass Spectrometry, Nickel Column, Western Blot, Size-exclusion Chromatography, SDS Page, Immunoprecipitation, Membrane, Purification, Staining, Software, Proximity Ligation Assay