Mechanisms of integrin αVβ5 clustering in flat clathrin lattices

Abstract

The family of integrin transmembrane receptors is essential for the normal function of multicellular organisms by facilitating cellextracellular matrix adhesion. The vitronectin-binding integrin αVβ5 localizes to focal adhesions (FAs) as well as poorly characterized flat clathrin lattices (FCLs). Here, we show that, in human keratinocytes, αVβ5 is predominantly found in FCLs, and formation of the αVβ5containing FCLs requires the presence of vitronectin as ligand, Ca 2+ , and the clathrin adaptor proteins ARH (also known as LDLRAP1), Numb and EPS15/EPS15L1. Integrin chimeras, containing the extracellular and transmembrane domains of β5 and the cytoplasmic domains of β1 or β3, almost exclusively localize in FAs. Interestingly, lowering actomyosin-mediated contractility promotes integrin redistribution to FLCs in an integrin tail-dependent manner, while increasing cellular tension favors αVβ5 clustering in FAs. Our findings strongly indicate that clustering of integrin αVβ5 in FCLs is dictated by the β5 subunit cytoplasmic domain, cellular tension and recruitment of specific adaptor proteins to the β5 subunit cytoplasmic domains.

Focal adhesion-generated cues in extracellular matrix regulate cell migration by local induction of clathrin-coated plaques

“…It was shown that their presence was cell type specific and that they were limited to the ventral plasma membrane 36 . This side-specific localization and the fact that clathrin-coated plaques are in close contact with the substrate 31,32 as well as associated with the ECM receptors integrins 27,32–34 strongly suggest a function in cell adhesion. Aiming at characterizing this function, we exploited the human glioblastoma U373 cell line previously reported to display clathrin-coated plaques 36,37 .…”

“…Previously, it was suggested that proteins of the clathrin pioneer module that initiate CME and lead to the recruitment of clathrin to the plasma membrane, e.g. FCHO1/2 and Eps15/R, stabilize the clathrin lattice early during coat formation and help to establish the hexagonal organization of flat clathrin structures 34,58–60 . Therefore, we investigated if early clathrin-related proteins of the pioneer module are important for clathrin-coated plaque formation.…”

“…The presence of clathrin-coated plaques at the ventral plasma membrane has been long known 36 . Recently, although their origin and function remained enigmatic, several studies have reported that the presence of clathrin-coated plaques at the plasma membrane was dependent on integrins 33,34 . These findings described that not only are integrins enriched at clathrin-coated plaques, but also describes that they are mandatory to stabilize flat clathrin arrays 27,33,34 .…”

“…Recently, although their origin and function remained enigmatic, several studies have reported that the presence of clathrin-coated plaques at the plasma membrane was dependent on integrins 33,34 . These findings described that not only are integrins enriched at clathrin-coated plaques, but also describes that they are mandatory to stabilize flat clathrin arrays 27,33,34 . This is consistent with our findings that interference with integrin binding to the ECM proteins impacts clathrin-coated plaque stability and induces their disassembly.…”

“…The putative role of larger clathrin arrays in cell adhesion and migration has long been discussed 31,32 . It has recently been readdressed with the observation that specialized clathrin arrays named tubular clathrin/AP2 lattices (TCALs) are responsible for binding collagen fibres in a 3D-environment 19 and that association of clathrin-coated plaques with the ECM is integrin dependent 27,33,34 .…”