Structural Diversity of Caveolins

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Flask shaped invaginations known as caveolae function as important regulators of cellular and physiological processes and have been linked to a number of diseases ranging from cardiovascular disorders to cancer. The caveolins, a family of monotopic membrane proteins, serve as fundamental building blocks of caveolae. Remarkably, caveolins have eluded high resolution characterization since their discovery in the early 1990s. This has made it nearly impossible to understand the exact mechanisms by which caveolae form and function or how defects in caveolae give rise to disease. To fill this critical gap in knowledge, we have assembled an investigative team consisting of experts in single particle electron microscopy, the structure of membrane proteins, computational analysis of protein structure, and the cell biology and biochemistry of caveolins. Our combined efforts have now led to the first atomic structure of human caveolin-1 (Cav1) assembled in an oligomeric form required for caveolae assembly, the 8S complex. This represents an enormous step forward for the field, which up until now has operated in the absence of definitive structural insights into how Cav1 oligomerize to form complexes or what regions of Cav1 are required to bind other proteins and lipids to build functional caveolae. Here, we propose to leverage our success in determining the structure of the Cav1 8S complexes to address a new series of questions about the structural and functional properties of this enigmatic protein family using a combination of structural, computational, biochemical, and cell biological approaches. First, we will interrogate the role of key residues and domains in controlling the formation and structure of human caveolin 8S complexes and its sensitivity to naturally occurring pathogenic mutations. Second, we will test the hypothesis that the ability of caveolins to assemble into membrane-associated oligomeric complexes capable of remodeling membranes is one of their most ancient functions by studying representative caveolins across the evolution. Third, we will probe the ability of structurally diverse caveolins, generated either as a consequence of genetic variability or evolutionary divergence, to support the biogenesis of functional caveolae. Successful completion of these studies will provide a much-needed framework to understand how Cav1 assembles into caveolae capable of ensuring proper function of multiple cell types and organ systems, how disease-associated mutations of Cav1 interfere with these processes in humans, and how evolution has harnessed this protein to accomplish its many roles in organisms across Metazoa and beyond.