Abstract
The fatty acid transport proteins (FATP) and long-chain acyl coenzyme A synthetase (ACSL) proteins have been shown to play a role in facilitating long-chain fatty acid (LCFA) transport in mammalian cells under physiologic conditions. The involvement of both FATP and ACSL proteins is consistent with the model of vectorial acylation, in which fatty acid transport is coupled to esterification. This study was undertaken to determine whether the functions of these proteins are coordinated through a protein-protein interaction that might serve as a point of regulation for cellular fatty acid transport. We demonstrate for the first time that FATP1 and ACSL1 coimmunoprecipitate in 3T3-L1 adipocytes, indicating that these proteins form an oligomeric complex. The efficiency of FATP1 and ACSL1 coimmunoprecipitation is unaltered by acute insulin treatment, which stimulates fatty acid uptake, or by treatment with isoproterenol, which decreases fatty acid uptake and stimulates lipolysis. Moreover, inhibition of ACSL1 activity in adipocytes impairs fatty acid uptake, suggesting that esterification is essential for fatty acid transport. Together, our findings suggest that a constitutive interaction between FATP1 and ACSL1 contributes to the efficient cellular uptake of LCFAs in adipocytes through vectorial acylation.
Highlights
The fatty acid transport proteins (FATP) and longchain acyl coenzyme A synthetase (ACSL) proteins have been shown to play a role in facilitating long-chain fatty acid (LCFA) transport in mammalian cells under physiologic conditions
We observed coimmunoprecipitation between ACSL1 and fatty acid transport protein 1 (FATP1), both immunoprecipitating with a-HA antibody followed by Western blot for native ACSL1 and immunoprecipitating with a-Myc antibody followed by Western blot for native FATP1
As expected, competing HA or Myc peptide inhibited immunoprecipitation as well as coimmunoprecipitation. These results indicate that FATP1 and ACSL1 participate in an oligomeric complex in 3T3-L1 adipocytes
Summary
The fatty acid transport proteins (FATP) and longchain acyl coenzyme A synthetase (ACSL) proteins have been shown to play a role in facilitating long-chain fatty acid (LCFA) transport in mammalian cells under physiologic conditions. A number of proteins have been suggested to facilitate or regulate fatty acid transport across the plasma membrane, including fatty acid transport protein 1 (FATP1) and long-chain acyl coenzyme A synthetase 1 (ACSL1) [6,7,8]. These proteins were identified in a functional screen for adipocyte proteins that augment cellular fatty acid import [9]. Black and colleagues [11] demonstrated coimmunoprecipitation between Fat1p and Faa1p or Faa4p, yeast orthologs of FATP1 and ACSL1, respectively
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