Interaction of cavin-1/PTRF leucine zipper domain 2 and its congenital generalized lipodystrophy mutant with model membranes.

The organization of caveolae ultrastructures in the plasma membrane and the functions they dictate are mediated by membrane-embedded caveolins (caveolin-1, 2, 3) and peripherally attached cavins (cavin-1, 2, 3, 4). Mutations in caveolin and cavin genes are associated with a variety of human diseases. Cavin-1/PTRF mutations are known to contribute to several human pathologies, including muscular dystrophy and congenital generalized lipodystrophy (CGL). In the present study, we investigated the membrane interaction of the second leucine zipper domain (LZD2) of cavin-1 and the analogous peptide stretch in its CGL frameshift mutant (p.Glu176Argfs). The fluorescence data from the Trp-tagged peptides suggest binding of both wild-type and mutant peptide with negatively-charged membranes. The mutant peptide displayed a rather enhanced interaction compared to the wild-type peptide. In addition, the mutant peptide displayed appreciable binding to the lipid raft-mimicking cholesterol/sphingomyelin-rich vesicles as well. The alteration in the dynamics of peptide-lipid interaction is attributed to increased charge and hydrophilicity of the mutant peptides. Overall, these results suggest that the frameshift mutation in cavin-1/PTRF (p.Glu176Argfs) imparts high membrane-binding propensity to the region corresponding to LZD2, which is hitherto unknown to interact with membranes. Such interaction in the disease condition, in turn, could either alter the native membrane interaction dynamics of cavin-1/PTRF or possibly result in interaction with non-target membranes.