A Molecular Dissection of Caveolin-1 Membrane Attachment and Oligomerization. TWO SEPARATE REGIONS OF THE CAVEOLIN-1 C-TERMINAL DOMAIN MEDIATE MEMBRANE BINDING AND OLIGOMER/OLIGOMER INTERACTIONS IN VIVO (original) (raw)

2000, Journal of Biological Chemistry

Caveolins form interlocking networks on the cytoplasmic face of caveolae. The cytoplasmically directed N and C termini of caveolins are separated by a central hydrophobic segment, which is believed to form a hairpin within the membrane. Here, we report that the caveolin scaffolding domain (CSD, residues 82-101), and the C terminus (residues 135-178) of caveolin-1 are each sufficient to anchor green fluorescent protein (GFP) to membranes in vivo. We also show that the first 16 residues of the C terminus (i.e. residues 135-150) are necessary and sufficient to attach GFP to membranes. When fused to the caveolin-1 C terminus, GFP co-localizes with two trans-Golgi markers and is excluded from caveolae. In contrast, the CSD targets GFP to caveolae, albeit less efficiently than full-length caveolin-1. Thus, caveolin-1 contains at least two membrane attachment signals: the CSD, dictating caveolar localization, and the C terminus, driving trans-Golgi localization. Additionally, we find that caveolin-1 oligomer/oligomer interactions require the distal third of the caveolin-1 C terminus. Thus, the caveolin-1 C-terminal domain has two separate functions: (i) membrane attachment (proximal third) and (ii) protein/protein interactions (distal third). Caveolae are flask-shaped invaginations of the plasma membrane that are found in most cell types. However, caveolae are most abundant in endothelial cells, adipocytes, epithelial cells, fibroblasts, and myocytes (1). These structures participate in three main areas of cell physiology: endocytosis (2), cholesterol traffic (3), and signal transduction (4). They are coated on their cytoplasmic face by a family of proteins, the caveolins. Three mammalian caveolin genes (caveolin-1,-2, and-3) have been identified and characterized (5). Whereas caveolin-1 and-2 have overlapping tissue distributions (6), caveolin-3 is limited to muscle and neuroglial cells (7-10). Although expression of caveolin-1 or-3 is sufficient to form caveolae in cells lacking these structures (11-14), caveolins are