INTRODUCTION: Adhesion at the podocyte-extracellular matrix (ECM) interface is essential for glomerular filtration barrier integrity. Podocytes adhere to laminin-521 within the glomerular basement membrane via integrin α3β1 and evidence suggests that podocyte attachment to type IV collagen is upregulated in disease states. However, the mechanisms by which adhesion to different ECM ligands produce distinct cellular phenotypes are poorly understood. Here we aimed to gain a holistic understanding of ECM-specific podocyte adhesion signalling by analysing isolated podocyte integrin adhesions complexes (IACs) using global mass spectrometry (MS)-based proteomics

METHODS: We analysed podocyte morphology following engagement with either laminin-521 or type IV collagen (α1α1α2) and isolated basolateral IACs for analysis by MS. We performed downstream bioinformatic analyses to define, for the first time, the podocyte adhesome following engagement with laminin and type IV collagen.

RESULTS: Human podocytes cultured on type IV collagen spread rapidly in an unpolarised manner forming radial actin stress fibres. By comparison, elongated cells with multiple lamellipodia and filopodia-like projections were formed on laminin-521. MS of isolated IACs from podocytes revealed that their composition was determined by ECM ligand. This phenomenon was cell-type specific; retinal pigment epithelial cell derived IACs displayed ECM dependent compositional changes that were distinct from those observed in podocytes. MS and protein interaction network mapping highlighted PKCα as a key signalling point controlling podocyte morpholgy downstream of ECM ligand engagement.

CONCLUSIONS: We discovered that ECM ligand influences podocyte morphology, adhesion complex composition and intracellular signalling. Enhanced understanding about the pathways that control podocyte adhesion may ultimately inform therapeutic strategies to correct or repair glomerular barrier function.