Novel role of FATP1 in mitochondrial fatty acid oxidation in skeletal muscle cells

Abstract

Carnitine palmitoyltransferase 1 (CPT1) catalyzes the first step in long-chain fatty acid import into mitochondria, and it is believed to be rate limiting for β-oxidation of fatty acids. However, in muscle, other proteins may collaborate with CPT1. Fatty acid translocase/CD36 (FAT/CD36) may interact with CPT1 and contribute to fatty acid import into mitochondria in muscle. Here, we demonstrate that another membrane-bound fatty acid binding protein, fatty acid transport protein 1 (FATP1), collaborates with CPT1 for fatty acid import into mitochondria. Overexpression of FATP1 using adenovirus in L6E9 myotubes increased both fatty acid oxidation and palmitate esterification into triacylglycerides. Moreover, immunocytochemistry assays in transfected L6E9 myotubes showed that FATP1 was present in mitochondria and coimmunoprecipitated with CPT1 in L6E9 myotubes and rat skeletal muscle in vivo. The cooverexpression of FATP1 and CPT1 also enhanced mitochondrial fatty acid oxidation, similar to the cooverexpression of FAT/CD36 and CPT1. However, etomoxir, an irreversible inhibitor of CPT1, blocked all these effects. These data reveal that FATP1, like FAT/CD36, is associated with mitochondria and has a role in mitochondrial oxidation of fatty acids.

Increasing skeletal muscle fatty acid transport protein 1 (FATP1) targets fatty acids to oxidation and does not predispose mice to diet-induced insulin resistance

“…Although it has been observed that FATP1 resides on mitochondrial membranes in myotubes, regulating LCFA oxidation in an unknown manner [40], this is not supported by findings of the present study in mature mammalian muscle. In mitochondria isolated Basal glucose values were generated in non-fasting condition † p=0.056…”

“…A recent report on L6E9 myotubes suggests that FATP1 is also present on mitochondrial membranes, where it regulates the rate of mitochondrial LCFA oxidation [40]. To determine whether the increase in palmitate oxidation observed at the whole-muscle level was a result of intracellular lipid trafficking or due to changes in mitochondrial FATP1 protein, we measured palmitate oxidation and FATP1 protein content in isolated SS and IMF mitochondria in control and Fatp1-transfected muscles.…”

“…To our knowledge, Fatp1 does not contain a mitochondrial targeting sequence, and we did not include a targeting sequence in our vector. Other investigators also omitted a mitochondrial targeting sequence when upregulating mitochondrial Fatp1 in L6E9 cells [40]. While the lack of a targeting sequence in the current study may partially explain negative findings at the mitochondria level, we have previously used identical methods to overexpress Fabppm (also known as Got2), which also does not contain a mitochondrial targeting sequence, resulting in increased FABPpm levels on sarcolemmal and mitochondrial membranes [26].…”

Delineating the role of alterations in lipid metabolism to the pathogenesis of inherited skeletal and cardiac muscle disorders

“…by guest, on www.jlr.org Downloaded from acyl-CoAs, the outer membrane enzyme CPT1 catalyzes the conversion of long-chain fatty acyl-CoAs to acylcarnitines, which then translocate across the inner mitochondrial membrane through the action of carnitine-acylcarnitine translocase (61)(62)(63). In the fi nal step, acylcarnitines are converted back to their corresponding acyl-CoAs by CPT2, allowing for ␤ -oxidation to proceed (61)(62)(63).…”

“…In the fi nal step, acylcarnitines are converted back to their corresponding acyl-CoAs by CPT2, allowing for ␤ -oxidation to proceed (61)(62)(63). The three isoforms of CPT1 are expressed phospholipids, or stored as triacylglycerol (TG) ( Fig.…”