DHHC4 And DHHC5 Facilitate Fatty Acid Uptake By Palmitoylating CD36

Protein S-palmitoylation is a post-translational modification in eukaryotic proteins,and it is the covalent attachment of the palmitoyl group to the thiol group of a Cys residue.The reaction is catalyzed by a family of palmitoyl acyltransferases,which contained a conserved Asp-His-His-Cys(DHHC)motif in the active site.Protein palmitoylation provides a key regulatory mechanism for multiple protein functions,including protein targeting,trafficking and stability.Currently,studies in DHHCs have been mainly focusing on their roles in cancer and neuron systems;however,the function of DHHCs in regulating is largely unknown.As adipose tissue is specialized to store fatty acids,we wondered whether palmitoylation,a fatty acyl modification,would play a role in regulating the physiological functions of adipose tissues.We analyzed the expression profiles of the 24 DHHCs in mouse white and brown adipose tissues(WAT and BAT)by quantitative real-time PCR.We found that Dhhc2,Dhhc4,Dhhc5,Dhhc6,Dhhc7 and Dhhc20 are relatively abundant in adipose tissues.We started with identifying the potential substrates of DHHC5 using the BioID technique,and found CD36 as a potential candidate.CD36 is one of the scavenger receptors,also known as a fatty acid translocase,and it plays an essential role in fatty acid uptake in adipose tissues and muscle.Acyl-RAC analysis confirmed that CD36 is a physiological substrate of DHHC5.We then identified DHHC4 as the other palmitoylating enzyme for CD36.Knockdown of either of them in preadipocytes or adipocytes dissociated CD36 from the plasma membrane and abolished its fatty acid uptake activity.While DHHC4 palmitoylates CD36 at the Golgi and creates a sorting signal for CD36 to the plasma membrane,DHHC5 at the plasma membrane maintains CD36 at the cell surface by preventing depalmitoylation of CD36.To further study the physiological roles of DHHC4 and DHHC5,we generated whole-body Dhhc4 knockout and adipose tissue specific Dhhc5 knockout mice.Both strains of mice show decreased fatty acid uptake activity in adipose tissues and develop severe hypothermia upon acute cold exposure.Our studies have thus uncovered an essential role of DHHC4 and DHHC5 in regulating fatty acid uptake by palmitoylating and targeting CD36 to the plasma membrane,and provide insights into research on the lipid metabolism of DHHC family.