Abstract

Rab18 has been linked to lipid metabolism and metabolic diseases in different model systems, but the mechanism of Rab18-mediated lipid droplet (LD) dynamics in muscle cells remains elusive. Here, we report that Rab18 plays an essential role in oleic acid (OA)-induced LD growth and formation in mouse myoblast cell line C2C12. Rab18 was translocated from endoplasmic reticulum (ER) to LDs during the LD growth induced by OA in C2C12 cells, which was directly regulated by perilipin 2 (PLIN2), a LD resident protein. LD-associated Rab18 bound with the C terminus of PLIN2, and the LD localization of Rab18 was diminished after PLIN2 deletion. Moreover, loss of function of Rab18 led to less triacylglycerol (TAG) accumulation and fewer but larger LD formation. In contrast, expression of wild type Rab18 and a constitutively active Rab18 (Q67L) mutant resulted in elevated TAG content and LD number. Furthermore, LD-associated Rab18 interacted with acyl-CoA synthetase long-chain family member 3 (ACSL3) and in turn, promoted the LD localization of ACSL3, which may play an important role in the accumulation of TAG induced by OA. These data showed that Rab18 was recruited to LD after OA treatment, and formed a complex with PLIN2 and ACSL3, which contributes to TAG accumulating and LD growth.