Membrane Curvature and Tension Control the Formation and Collapse of Caveolar Superstructures

Abstract

Caveolae, flask-shaped pits covered by caveolin-cavin coats, are abundant features of the plasma membrane of many cells. Besides appearing as single-membrane indentations, caveolae are organized as superstructures in the form of rosette-like clusters, whose mechanism of assembly and biological functions have been elusive. Here, we propose that clustering of caveolae in mature muscle cells is driven by forces originating from the elastic energy of membrane-bending deformations and membrane tension. We substantiate this mechanism by computational modeling, which recovers the unique shapes observed for the most ubiquitous caveolar clusters. We support the agreement between the calculated and observed configurations by electron tomography of caveolar clusters. The model predicts the experimentally assessable dependence of caveolar clustering on membrane tension and on the degree of the caveolar coat assembly. We reveal a difference in conformation and, possibly, in function and formation mechanism between caveolar clusters of muscle cells and of adipocytes.

Keywords: caveolae; caveolar clusters; mechano-protective function; membrane bending elasticity; membrane curvature; membrane tension; membrane-mediated interaction; modeling caveolae.