Fig. 7.

ECM influences EPB41L5-mediated phenotypes. (A) Cell morphology assessed as major–minor axis quantification revealed altered morphological appearance of EPB41L5 KO cells on collagen compared with fibronectin conditions (at least 145 cells were analyzed, averaged more than three independent experiments; Dataset S3). (B, C, D–J) EPB41L5 KO clones show defective ECM sensing on collagen IV coated substratum. In contrast, increasing concentrations of the ECM ligand fibronectin led to improved spreading in respective KO clones (at least 100 cells per genotype and condition were analyzed, averaged over three independent experiments; Dataset S3). (K) Map of SILAC-based quantitative EPB41L5 dependent focal adhesome. (L) Western blot confirmation of focal adhesome fraction revealing balanced levels for PAXILLIN, whereas ITGB1, ITGA2, and also ARHGEF18 showed decreased intensity compared with the wild-type. (M) Schematic summarizing the phenotypic features of the EPB41L5 knockout characterized by foot process effacement and pronounced podocyte detachment. (N) EPB41L5 modulates actomyosin contractility via direct recruitment of the small GTPase ARHGEF18, and thereby influences FA maturation. This process is influenced via ECM composition and potential regulatory roles mediated by collagen receptors. Coll, collagen IV; ECM, extracellular matrix; FA, focal adhesion; FN, fibronectin, NM-II, nonmuscle myosin 2; SD, slit diaphragm; SILAC, stable isotope labeling by amino acids in cell culture.