Regulation of autophagy by extracellular matrix glycoproteins in HeLa cells.
Macroautophagy is a major lysosomal degradation pathway for cellular components in eukaryotic cells. Baseline macroautophagy is important for quality control of the cytoplasm in order to avoid the accumulation of cytotoxic products. Its stimulation by various stressful situations, including nutrient starvation, is important in maintaining cell survival. Here we demonstrate that macroautophagy is regulated differently depending on whether HeLa cells adhere to collagen I or collagen IV, proteins typical of connective tissue and basal membrane, respectively. We observed that the basal levels of macroautophagy were higher in cells plated on collagen IV than in cells plated on collagen I or on uncoated substrate. However, the stimulation of macroautophagy by nutrient starvation, as reflected by the buildup of autophagosomes and the increase in the autophagic flux, was higher in cells plated on collagen I than in cells plated on collagen IV. These contrasting results were not due to differences in the starvation-dependent inhibition of mTOR complex 1 signaling. Interestingly, cells plated on collagen IV formed numerous focal adhesions (FAs), whereas fewer FAs were observed in cells plated on the other substrates. This implies that focal adhesion kinase (FAK) was more robustly activated by collagen IV. Silencing the expression of FAK by siRNA in cells plated on collagen IV shifted the autophagic phenotype of these cells to an "uncoated substrate autophagic phenotype" under both basal and starvation-induced conditions. Moreover, cells plated on collagen IV were less dependent on autophagy to survive in the absence of nutrients. We conclude that extracellular matrix components can modulate macroautophagy and mitigate its role in cell survival.
Tuloup-Minguez
Véronique
V
INSERM UMR756 and Faculty of Pharmacie, University of Paris-Sud 11, Paris, France.
Greffard
Anne
A
Codogno
Patrice
P
Botti
Joëlle
J
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000818:Animals; D001343:Autophagy / Q000187:drug effects; D002417:Cattle; D002448:Cell Adhesion / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects; D048430:Cell Shape / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D024141:Collagen Type IV / Q000494:pharmacology; D016326:Extracellular Matrix Proteins / Q000378:metabolism*; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D022001:Focal Adhesions / Q000187:drug effects / Q000378:metabolism; D020868:Gene Silencing / Q000187:drug effects; D006023:Glycoproteins / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D016023:Integrins / Q000378:metabolism; D000076222:Mechanistic Target of Rapamycin Complex 1; D046912:Multiprotein Complexes; D010969:Plastics / Q000494:pharmacology; D011506:Proteins / Q000378:metabolism; D000071456:Sequestosome-1 Protein; D015398:Signal Transduction / Q000187:drug effects; D058570:TOR Serine-Threonine Kinases
D048868:Adaptor Proteins, Signal Transducing; D024141:Collagen Type IV; D016326:Extracellular Matrix Proteins; D006023:Glycoproteins; D016023:Integrins; D046912:Multiprotein Complexes; D010969:Plastics; D011506:Proteins; C099718:SQSTM1 protein, human; D000071456:Sequestosome-1 Protein; D051416:Focal Adhesion Protein-Tyrosine Kinases; D000076222:Mechanistic Target of Rapamycin Complex 1; D058570:TOR Serine-Threonine Kinases