Loss of the Essential Autophagy Regulators FIP200 or Atg5 Leads to Distinct Effects on Focal Adhesion Composition and Organization

Abstract

Autophagy is an essential catabolic intracellular pathway that maintains homeostasis by degrading long-lived proteins, damaged organelles, and provides an energy source during nutrient starvation. It is now understood that autophagy has discrete functions as a selective lysosomal degradation pathway targeting large cytosolic structural and signaling complexes to influence cell motility and adhesion. We provide evidence suggesting the primary autophagy regulators Atg5 and FIP200 both play a role in cell motility and extracellular matrix adhesion. However, their loss of function has a differential impact on focal adhesion composition and organization, as well as signaling in response to fibronectin induced cell spreading. This differential impact on focal adhesions is illustrated by smaller focal adhesion complexes and a decrease in FAK, paxillin, and vinculin expression associated with FIP200 loss of function. In contrast, Atg5 loss of function results in production of large and stable focal adhesions, characterized by their retention of phosphorylated FAK and Src, which correlates with increased vinculin and FAK protein expression. Importantly, autophagy is upregulated during processes associated with focal adhesion reorganization and their exhibits colocalization of autophagosomes with focal adhesion cargo. Interestingly, FIP200 localizes to vinculin-rich focal adhesions and its loss negatively regulates FAK phosphorylation. These data collectively suggest FIP200 and Atg5 may have both autophagy-dependent and -independent functions that provide distinct mechanisms and impacts on focal adhesion dynamics associated with cell motility.

The adhesion GPCR VLGR1/ADGRV1 regulates focal adhesion turnover by controlling their assembly

“…We treated primary astrocytes derived from brains of Vlgr1-deficient Vlgr1/DrumB mutant mice or wild type (WT) mice with either DMSO or nocodazole (NDZ) (10 μM) in DMSO. Consistent with previous reports 24,28,29 , NDZ treatment induced microtubule depolymerization leading to cell-cycle synchronization and accumulation of FAs (Figures 2A, B). After replacing the NDZ medium by fresh medium without NDZ (NDZ washout) a phase of rapid FA disassembly was introduced which rested for approximately 45 min (Figures 2A, B).…”

SphK1‐driven autophagy potentiates focal adhesion paxillin‐mediated metastasis in colorectal cancer

“…34 Additionally, loss of ATG5 function made the expression of paxillin reduced, resulting in stable adhesion plaques and reduced directed cell motility, and autophagy enhanced FAK signaling and degraded paxillin to promote FA disassembly to suppress cell adhesion then resulted in less cell spreading. 35 The present study demonstrated that inhibition of paxillin was found in the SphK1 knockdown CRC cells in vitro and vivo, moreover, suppression of autophagy by 3MA reversed the expression of paxillin and its phosphorylation in SphK1overexpressed CRC cells. SphK1-driven autophagy may induce the assembly and disassembly of FA via regulating paxillin and its phosphorylation.…”

Exploring the influence of cytosolic and membrane FAK activation on YAP/TAZ nuclear translocation

“…In addition, other authors have reported that active FAK can be found in the cytoplasm (which we model in cases 1 and 2; see below), and even translocate from the cytoplasm to the nucleus ( 46 , 50 , 51 ). On the other hand, Emelia and Tumbarello ( 52 ) have shown that depletion of FIP200 and loss of Atg5 (two autophagosome regulators) lead to retention of active FAK at focal adhesions, which we model in cases 3 and 4 (see below).…”