Vesicle coat protein involved in Golgi to plasma membrane transport
In yeast cells this family functions in the regulated delivery of Gap1p (a general amino acid permease) to the cell surface, perhaps as a component of a post-Golgi secretory-vesicle coat complex. Birt-Hogg-Dube (BHD)4 syndrome is an autosomal dominant disorder characterized by hamartomas of skin follicles, lung cysts, spontaneous pneumothorax, and renal cell carcinoma. Folliculin is the protein from the BHD4 gene and is found to have no significant homology to any other human proteins. It is expressed in most tissues. These same symptoms also occur in TSC or tuberous sclerosis complex, suggesting that the same pathway is involved, and it is likely that the target is the down-stream Tor2 - an essential gene. Folliculin appears to bind Tor2, and down-regulation of Tor2 activity leads to up-regulation of nitrogen responsive genes including membrane transporters and amino acid permeases.