Long-chain acyl coenzyme A synthetase activity during the postnatal development of the mouse brain

Gene targets related to phospholipid and fatty acid metabolism in schizophrenia and other psychiatric disorders: an update

Phospholipids make up about 60% of the brain's dry weight and play key roles in many brain signal tranduction mechanisms. A recent review(1)identified the increasing evidence that abnormal phospholipid and related fatty acid metabolism may contribute to illnesses such as schizophrenia, bipolar disorder, depression and attention deficit hyperactivity disorder. This current paper reviews the main pathways of phospholipid metabolism, emphasizing the role of phospholipases of the A2 in signal tranduction processes. It also updates the chromosomal locations of regions likely to be involved in these disorders, and relates these to the known locations of genes directly or indirectly involved in phospholipid and fatty acid metabolism.

New gene targets related to schizophrenia and other psychiatric disorders: enzymes, binding proteins and transport proteins involved in phospholipid and fatty acid metabolism

Phospholipids make up about 60% of the brain's dry weight. In spite of this, phospholipid metabolism has received relatively little attention from those seeking genetic factors involved in psychiatric and neurological disorders. However, there is now increasing evidence from many quarters that abnormal phospholipid and related fatty acid metabolism may contribute to illnesses such as schizophrenia, bipolar disorder, depression and attention deficit hyperactivity disorder. To date the possible specific proteins and genes involved have been relatively ill-defined. This paper reviews the main pathways of phospholipid metabolism, emphasizing the roles of phospholipases of the A2 and C series in signal transduction processes. It identifies some likely protein candidates for involvement in psychiatric and neurological disorders. It also reviews the chromosomal locations of regions likely to be involved in these disorders, and relates these to the known locations of genes directly or indirectly involved in phospholipid and fatty acid metabolism.

Molecular characterization and expression of rat acyl-CoA synthetase 3

Isolation and characterization of a rat brain cDNA identified a third acyl-CoA synthetase (ACS) designated ACS3. The deduced amino acid sequence of the cDNA revealed that ACS3 consists of 720 amino acids and exhibits a structural architecture common to ACSs from various origins. ACS3 expressed in COS cells was purified to near homogeneity. The purified ACS3 resolved by SDS-polyacrylamide gel electrophoresis into two major proteins of 79 and 80 kDa. Cell-free translation of a synthetic mRNA encoding the entire region of ACS3 revealed that the two isoforms were derived from the same mRNA. The purified ACS3 utilizes laurate and myristate most efficiently among C8-C22 saturated fatty acids and arachidonate and eicosapentaenoate among C16-C20 unsaturated fatty acids. Northern blot analysis revealed that ACS3 mRNA is most abundant in brain and, to a much lesser extent, in lung, adrenal gland, kidney, and small intestine. During the development of the rat brain, expression of ACS3 mRNA reached a maximum level at 15 days after birth and then declined gradually to 10% of the maximum in the adult brain.

Postnatal changes in activation of polyunsaturated fatty acid, acylation of lysophosphoglyceride, and phosphorylation of diacylglycerol in cortical gray matter of rat cerebrum

Activation of polyunsaturated fatty acid, acylation of lysophosphoglyceride, and phosphorylation of diacylglycerol in postnatal developing rat cerebrum were studied in vitro, using cortical gray matter homogenates. The rate of n-3 and n-6 fatty acid activation was maximal at ten days after birth and minimal at adulthood. Acylation of lysophosphoglyceride was most active at the neonatal stage and gradually decreased with age. In addition, the amount of phosphatidic acid formed from 1, 2-dioleoyl-glycerol was also maximum at the neonatal stage, and then gradually decreased. These results suggest that the specific activity of glycerolipid synthesis in cortical gray matter declines during postnatal development.

Synthesis of docosahexaenoyl-, arachidonoyl- and palmitoyl-coenzyme A in ocular tissues

The synthesis of long-chain acyl coenzyme A (CoA) was studied in the cornea, lens, vitreous, retina and pigment epithelium (PE) in the rat using [14C]-labeled palmitic, arachidonic and docosahexaenoic acids as substrates. Except for retina and PE, the ocular tissues studied showed relatively little enzyme activity with the fatty acid substrates. In addition, the enzyme activities were studied in homogenates and microsomal fractions from retina, pigment epithelial cells and choroid of frog, bovine and human eyes. Long-chain acyl CoA synthetase from the microsomal fraction exhibited three- to fivefold greater activity than homogenates in retina and PE. The enzyme activity was highest with palmitic acid, followed by arachidonic acid and docosahexaenoic acid. There were significant differences in enzyme activity between the species. The apparent Km (microM) and Vmax [nmol min-1 (mg protein)-1] values for the enzyme in bovine retinal microsomes were 7.91 +/- 0.39 (S.E.) and 21.6 +/- 1.04, respectively, for palmitic acid substrate and 5.88 +/- 0.25 and 4.58 +/- 0.21, respectively, for docosahexaenoic acid substrate. These values for bovine pigment epithelial microsomes were 13.0 +/- 0.27 and 36.9 +/- 1.18, respectively, for palmitic acid and 15.8 +/- 0.40 and 13.2 +/- 0.56, respectively, for docosahexaenoic acid. The synthesis of acyl CoA may play a central role in controlling the availability of free arachidonic acid for eicosanoid formation and in the retention of polyunsaturated fatty acid families (18:2, n-6 and 18:3, n-3) within cells of ocular tissues, particularly retina and retinal PE.

Activation of polyunsaturated fatty acids by rat tissues in vitro

The conversion of labeled palmitic, linoleic, arachidonic and docosahexaenoic acids to their respective acyl CoA's was studied in homogenates and microsomes of rat tissues. The highest activity, both in homogenates and microsomes, was seen in liver and heart. There was moderate activity in retina, brain, lung, kidney and testes and the lowest activity was found in spleen. Docosahexaenoic acid was activated much less actively in heart tissue than the other fatty acids. In all tissues examined, the highest activation was observed with arachidonic acid and the lowest with docosahexaenoic acid. Except for liver, those tissues that contained high levels of docosahexaenoic acid also had the highest activation capacity for this fatty acid.

Arachidonic acid and other long-chain fatty acids in canine ceroid lipofuscinosis. Distribution in glycerolipids, metabolism, and pathophysiological correlations

Dogs with canine ceroid lipofuscinosis (CCL)+ show an abnormal EEG as early as 5 mo of age and exhibited either severe disorganization or very low amplitudes by 24 mo. Ceroid particles accumulate with age and, within neurons, have a unique characteristic appearance consisting of lamellar patterns enclosed by a single unit membrane. Although the etiology of their formation has not been fully elucidated, isolated particles are enriched in phospholipids. Our present studies have examined microsomal enzymes involved in phospholipid synthesis and turnover and demonstrate that the acyl group composition of cerebral lipids from animals with CCL is similar to that from controls. However, the activation of palmitic, linoleic, arachidonic, and docosahexaenoic acids into their Coenzyme A thiol ester forms was significantly lower in cerebral and cerebellar microsomes of the diseased dogs than in those of the controls. In addition, the incorporation of arachidonic acid into phospholipids was significantly decreased in affected animals. These results suggest that the metabolism of arachidonic acid plays an important role in the pathogenesis of ceroid lipofuscinosis.