Evidence for phosphorylation/dephosphorylation of rat liver acyl-CoA:cholesterol acyltransferase.

Gavey, K L; Trujillo, Denise L.; Scallen, Terence J.

doi:10.1073/pnas.80.8.2171

Cited by 50 publications

(16 citation statements)

References 17 publications

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“…The regulation of enzyme activity could be achieved at several levels. For example, mammalian acylCoA:cholesterol acyltransferase activity is primarily controlled by protein phosphorylation (Gavey et al, 1983). A possible reason for the significant increase in oil content in the SLC7-7 transgenic Brassicaceae may be the result of differences in sn-2 acyltransferase regulation.…”

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confidence: 99%

Modification of seed oil content and acyl composition in the brassicaceae by expression of a yeast sn-2 acyltransferase gene.

et al. 1997

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A putative yeast sn-2 acyltransferase gene (SLC7-7), reportedly a variant acyltransferase that suppresses a genetic defect in sphingolipid long-chain base biosynthesis, has been expressed in a yeast SLC deletion strain. The SLC7-7 gene product was shown in vitro to encode an sn-2 acyltransferase capable of acylating sn-1 oleoyl-lysophosphatidic acid, using a range of acyl-COA thioesters, including 181-, 22:l-, and 240-COAS. The SLC7-7 gene was introduced into Arabidopsis and a high erucic acid-containing Brassica napus cv Hero under the control of a constitutive (tandem cauliflower mosaic virus 35s) promoter. The resulting transgenic plants showed substantial increases of 8 to 48% in seed oil content (expressed on the basis of seed dry weight) and increases in both overall proportions and amounts of very-long-chain fatty acids in seed triacylglycerols (TAGs). Furthermore, the proportion of very-long-chain fatty acids found at the sn-2 position of TAGs was increased, and homogenates prepared from developing seeds of transformed plants exhibited elevated lysophosphatidic acid acyltransferase (EC 2.3.1 51) activity. Thus, the yeast sn-2 acyltransferase has been shown to encode a protein that can exhibit lysophosphatidic acid acyltransferase activity and that can be used to change total fatty acid content and composition as well as to alter the stereospecific acyl distribution of fatty acids in seed TAGS.

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confidence: 99%

Modification of seed oil content and acyl composition in the brassicaceae by expression of a yeast sn-2 acyltransferase gene.

et al. 1997

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“…We recently reported the activations of rat aortic acid CEH (ACEH) and NCEH by both PKA and PKC to a similar extent in the presence of respective cofactors using selective inhibitors of two kinases (9). A cholesterol-esterifying enzyme, ACAT, is an integral membrane protein located in the endoplasmic reticulum, and evidence currently available for the involvement of phosphorylation in regulating ACAT is controversial; the dependence of ACAT activity on cholesterol availability has been documented in several studies (10,11): some evidence suggests the activation of ACAT by phosphorylation (12,13), whereas other evidence against the regulation of ACAT by phosphorylation has been presented (14,15).…”

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Effects of passive smoking on the regulation of rat aortic cholesteryl ester hydrolases by signal transduction

Maehira

Zaha

Miyagi

et al. 2000

Lipids

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The effects of exogenous oxidative stress due to passive smoking on cholesteryl ester (CE)-metabolizing enzymes and their regulatory kinases were examined by exposing rats to cigarette smoke (CS) for a 1-h period twice a day for 8, 12, or 20 wk. An oxidatively modified low density lipoprotein (Ox-LDL) with a high lipid peroxide was identified in three CS groups after all three exposure periods. The rat aortic acid and neutral CE hydrolases (ACEH and NCEH) were activated to similar extents by both cAMP-dependent protein kinase (PKA) and protein kinase C (PKC) in the presence of their respective cofactors. The aortic PKC activity in the three CS groups exhibited significant reductions of 72, 84, and 75% as compared with the respective controls, which coincided with the reductions in the ACEH activities (86, 71, and 80%, respectively), whereas the PKA activities increased to 121, 197, and 252% in the three CS groups, respectively. Reflecting the increase of the PKA activity, the NCEH activity exhibited increases of 112% at 8 wk and 140% until 12 wk of exposure and decreased by 50% of the control value at 20 wk of exposure, suggesting inactivation of NCEH itself. The activation of acyl-CoA:cholesterol O-acyltransferase activity was associated with an increase of free cholesterol in aorta. The vitamin E diet prevented the formation of Ox-LDL and the oxidative inactivation of most enzymes, especially PKC, until 12 wk, but was less effective by 20 wk. The oxidative inactivation of PKC, particularly its activated form that translocated to the membrane fraction, was confirmed in the in vitro exposure to active oxygen generators at an optimal concentration; this inactivation was prevented by catalase and superoxide dismutase. These results suggested that the formation of Ox-LDL and alterations in CE-metabolizing enzymes caused by passive smoking could contribute to a twofold increase in the aortic CE content, thereby contributing to one of the mechanisms for atherosclerosis associated with smoking.

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“…Studies with fibroblasts have shown that Ca2+-and phospholipid-dependent protein kinase C, which is activated by stimulation ofPtdIns turnover, controls the activity ofcertain enzymes involved in cellular LDL cholesterol (LDL-Chol) metabolism (3)(4)(5). This suggests an interrelationship between the PtdIns response and LDL-Chol metabolism, but it is not known whether low concentrations of LDL stimulate the PtdIns cycle in cells other than platelets.…”

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Low density lipoprotein causes general cellular activation with increased phosphatidylinositol turnover and lipoprotein catabolism.

Block

Knorr

Vogt

et al. 1988

Proc. Natl. Acad. Sci. U.S.A.

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Low density lipoprotein (LDL), at concentrations high enough for receptor binding but not high enough to saturate the receptor, induces activation of phosphatidylinositot (PtdIns) turnover in a variety of cell types with various biological functions. Using both biochemical and electron microscopic studies, we have shown that blood platelets take up and degrade LDL in a manner reminiscent of phagocytic cell types. The activation of both PtdlIns turnover and LDL metabolism is inhibited by high density lipoprotein. Thus, LDL at hormonal concentrations causes general cellular activation.Since all cell types studied responded to LDL with increased PtdIns turnover and uptake of LDL cholesterol, the PtdIns cycle may also be involved in the cellular regulation of LDL cholesterol metabolism.It has recently been demonstrated that low density lipoprotein (LDL), at concentrations in the range of its dissociation constant (Kd) for receptor binding, =1 nM, rapidly affects human platelets in several ways: (i) their shape and ultrastructural morphology are transiently altered; (ii) phosphatidylinositol (PtdIns) turnover and the molar concentration of intracellular free calcium, [Ca2+]i, are increased; and (iii) thromboxane B2 formation is enhanced (1). All of these effects are inhibited by high density lipoprotein fraction 3 (HDL3), which is known to interfere with LDL binding in platelets (2).Studies with fibroblasts have shown that Ca2+-and phospholipid-dependent protein kinase C, which is activated by stimulation ofPtdIns turnover, controls the activity ofcertain enzymes involved in cellular LDL cholesterol (LDL-Chol) metabolism (3-5). This suggests an interrelationship between the PtdIns response and LDL-Chol metabolism, but it is not known whether low concentrations of LDL stimulate the PtdIns cycle in cells other than platelets. Furthermore, it remains to be clarified whether platelets, like other cells, are capable of metabolizing LDL-Chol. Although platelets, which freely exchange cholesterol with plasma under normocholesteremic conditions, are unable to synthesize cholesterol, there is an unexplained increase in the cholesterol-phospholipid ratio in familial and experimental hypercholesterolemia (6-9). Also HDL fractions are known to be internalized and degraded by platelets (10). These findings suggested to us that there might be a catabolic pathway for LDL-Chol in the platelets.We show here that the LDL-induced activation of the PtdIns cycle occurs not only in platelets but also in various cell types that metabolize LDL-Chol, including arterial smooth muscle cells, lung fibroblasts, lymphocytes, and vascular endothelial cells. We also establish that the catabolism of lipoproteins occurs not only in these cell types but also in platelets. Thus, LDL induces general cellular activation at concentrations near the Kd for receptor binding, which appears to be comparable to hormonal effects. MATERIALS AND METHODSLipoprotein Isolation. LDL (density, 1.019-1.063 g/ml) and HDL3 (density, 1.125-1.3 g/ml) were isolate...

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Evidence for phosphorylation/dephosphorylation of rat liver acyl-CoA:cholesterol acyltransferase.

Cited by 50 publications

References 17 publications

Modification of seed oil content and acyl composition in the brassicaceae by expression of a yeast sn-2 acyltransferase gene.

Modification of seed oil content and acyl composition in the brassicaceae by expression of a yeast sn-2 acyltransferase gene.

Effects of passive smoking on the regulation of rat aortic cholesteryl ester hydrolases by signal transduction

Low density lipoprotein causes general cellular activation with increased phosphatidylinositol turnover and lipoprotein catabolism.

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