Mechanotransduction of matrix stiffness in regulation of focal adhesion size and number: reciprocal regulation of caveolin-1 and ?1 integrin.

ABSTRACT: Focal adhesion (FA) assembly, mediated by integrin activation, responds to matrix stiffness; however, the underlying mechanisms are unclear. Here, we showed that ?1 integrin and caveolin-1 (Cav1) levels were decreased with declining matrix stiffness. Soft matrix selectively downregulated ?1 integrin by endocytosis and subsequent lysosomal degradation. Disruption of lipid rafts with methyl-?-cyclodextrin or nystatin, or knockdown of Cav1 by siRNA decreased cell spreading, FA assembly, and ?1 integrin protein levels in cells cultured on stiff matrix. Overexpression of Cav1, particularly the phospho-mimetic mutant Cav1-Y14D, averted soft matrix-induced decreases in ?1 integrin protein levels, cell spreading, and FA assembly in NMuMG cells. Interestingly, overexpression of an auto-clustering ?1 integrin hindered soft matrix-induced reduction of Cav1 and cell spreading, which suggests a reciprocal regulation between ?1 integrin and Cav1. Finally, co-expression of this auto-clustering ?1 integrin and Cav1-Y14D synergistically enhanced cell spreading, and FA assembly in HEK293T cells cultured on either stiff (?>?G Pa) or soft (0.2 kPa) matrices. Collectively, these results suggest that matrix stiffness governs the expression of ?1 integrin and Cav1, which reciprocally control each other, and subsequently determine FA assembly and turnover.

SUBMITTER: Yeh YC 

PROVIDER: S-EPMC5678369 | biostudies-literature | 2017 Nov

REPOSITORIES: biostudies-literature