Acyl-CoA synthetase 2 overexpression enhances fatty acid internalization and neurite outgrowth.

Joseph R Marszalek,Claire Kitidis,Ariya Dararutana,Harvey F Lodish

doi:10.1074/jbc.m313460200

Abstract

During neurodevelopment neurons increase phospholipid synthesis to generate additional plasma membrane that makes up the growing neurites. Compared with most cell types, neurons contain a high percentage of the polyunsaturated fatty acids (PUFAs) arachidonic acid (AA) and docosahexaenoic acid (DHA). By utilizing PC12 cell lines as a model neuronal cell line, we examined the internalization rate of AA, DHA, and non-essential oleic acid (OA), as well as their effects on neurite outgrowth. When wild type cells were differentiated, the rate of AA and DHA internalization increased 50% more than the rate of OA internalization. When media were supplemented with AA or DHA, the average neurite length was increased by approximately 40%, but supplementation with the same amount of OA had no effect. We also increased the levels of acyl-CoA synthetase-1 (ACS1) and ACS2 proteins to determine whether they contribute to PUFA internalization or neurite outgrowth. Overexpression of ACS1 increased the rate of OA internalization by 55%, and AA and DHA uptake was increased by 25%, but there was no significant change in neurite outgrowth. In ACS2-overexpressing cells, in contrast, the rate of OA internalization increased by 90%, AA by 115%, and DHA by 70%. The average aggregate neurite length in ACS2-overexpressing cells was increased by approximately 40% when the media were supplemented with PUFAs, but there was no change with OA supplementation. Taken together, these results support the hypotheses that ACSs are rate-limiting for fatty acid internalization and that ACS2 enhances neurite outgrowth by promoting PUFA internalization.

Highlights

Fatty acids (FAs)1 are utilized by the body as an energy source, function as signaling molecules, and are a structural
Overexpression of acyl-coenzyme A (CoA) synthetase-1 (ACS1) increased the rate of oleic acid (OA) internalization by 55%, and arachidonic acid (AA) and docosahexaenoic acid (DHA) uptake was increased by 25%, but there was no significant change in neurite outgrowth
To confirm that the short term FA uptake assays presented in Fig. 1 measured FA internalization and not FA binding to the plasma membrane, undifferentiated and 3-day differentiated PC12 cells were incubated for 2 min with 5 ␮M radiolabeled OA, AA, or DHA, and the metabolic fates of these FAs were determined by TLC and scintillation counting

Summary

Introduction

Fatty acids (FAs) are utilized by the body as an energy source, function as signaling molecules, and are a structural. During differentiation neurons require substantial amounts of FAs for phospholipid (PL) synthesis to generate extensive neurites that are the morphological and physiological hallmarks of these cells This process utilizes FA from two sources: de novo FA synthesis through the action of the enzyme fattyacid synthase and uptake of essential FAs, which cannot be synthesized by mammals because they lack the desaturase enzymes that introduce double bonds at the n-3 and n-6 positions [1]. FAs can be utilized as a signaling molecule, constructively for PL and TAG synthesis or destructively as an energy source via ␤-oxidation These processes are believed to occur within specific regions of the cell and may be influenced by the subcellular localization of specific ACS isoforms [14]

Methods

Results

Conclusion