Fatty Acid Transporters in Animal Cells

The mechanism by which fatty acids transverse the plasma membrane has been a controversial subject. Kinetic studies of fatty acid uptake suggested the presence of a protein carrier system in certain cells which exhibit rapid fatty acid influx and/or efflux such as hepatocytes, adipocytes and jejunal mucosal cells. Five plasma membrane proteins have been identified and proposed as candidates for fatty acid transporters thus far. These includes: Plasma Membrane Fatty Acid Binding Protein (FABPpm), Fatty Acid Translocase (FAT), caveolin, a 56-kDa renal fatty acid binding protein and Fatty Acid Transport Protein (FATP). The first four proteins were identified by classical biochemical techniques while FATP, the one most recently reported, was identified by expression cloning strategies. Each of these proteins has distinct primary amino acid sequence and tissue-specific pattern of expression. It remains to be determined whether the proteins identified to date function as individual polypeptides or as a single component of a larger complex. This review summarizes recent advances concerning the structure, function and regulation of these putative fatty acid transporters.