ISSN:
1573-6903
Keywords:
Long chain acyl-CoA synthetase
;
fatty acid
;
glycerolipid
;
nerve growth factor
;
triacsin C
;
PC12 cells
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Using PC12 cells undergoing neurite outgrowth, we studied the activation of various fatty acids, of different chain lengths and degrees of saturation, by long chain acyl-CoA synthetases (LCASs). Cells treated with nerve growth factor (NGF) were labeled with [3H]glycerol, [3H]oleic acid (OA) or [3H]arachidonic acid (AA) in the presence of other unlabeled fatty acids of endogenous or exogenous origin. Triacsin C (4.8 μM), an inhibitor of acyl-CoA synthetase, decreased the incorporation of exogenous [3H]OA into glycerolipids by 30–90%, and increased by about 60% the accumulation of free [3H]OA in the cells. However it did not affect the incorporation of endogenous fatty acids nor of exogenous [3H]AA into phospholipids, suggesting that LCASs which activate exogenous AA and at least some endogenous fatty acids are relatively insensitive to this drug. Activities of the LCAS that is specific for AA (ACS), or of the non-specific LCAS which activates OA and other fatty acids (OCS), were much higher in microsomal and cytoplasmic fractions than in mitochondria or nuclei. The Vmax and Km values of ACS and OCS in microsomes were 12 and 0.7 nmol/min/mg protein and 70 and 37 μM, respectively; and in cytoplasm, 6 and 0.6 nmol/ min/mg protein and 38 and 60 μM, respectively. Triacsin C (2–33 μM) did not affect ACS activity in microsomal or cytoplasmal fractions, but inhibited OCS activities dose-dependently and competitively: IC50 and apparent Ki values were 13.5 μM and 14 μM in microsomes, and 3.8 μM and 4 μM in cytoplasm. NGF stimulated the activities of the LCASs, and, consistently, the incorporation of the various fatty acids into glycerolipids. These data indicate that LCASs are heterogeneous with respect to their intracellular locations, substrate specificities, kinetic characteristics and sensitivities to triacsin C; and that this heterogeneity affects the extents to which individual fatty acids are utilized to form glycerolipids.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1020727429052
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