Inhibition of protein tyrosine kinase alters the effect of serum basic protein I on triacylglycerols and cholesterol differently in normal and hyperapoB fibroblasts.
We studied whether the stimulatory effect of human serum basic protein I (BP I) on the formation of cell triacylglycerols and cholesterol may be mediated through protein tyrosine kinase in normal fibroblasts, and whether there was a deficiency in such a process in cells from subjects with hyperapobetalipoproteinemia (hyperapoB). Genistein, a highly specific inhibitor of tyrosine kinase phosphorylation, was used as a probe. When BP I (428.0 nmol/L) alone was added to F-12 medium without genistein, the mean mass of cell triacylglycerols doubled in six normal cell lines from healthy subjects, an effect that was decreased by 50% in six cell lines from subjects with hyperapoB (P = .007). The addition of genistein with BP I to normal cells decreased the stimulation of triacylglycerol formation by BP I by about 50% (P = .008), whereas genistein had little effect in the BP I-treated hyperapoB cells. The effect of genistein on the stimulation of triglyceride and cholesterol production by BP I was shown to be both time and concentration (92.5 nmol/mL medium nadir) dependent. In normal fibroblasts. BP I stimulated the rate of incorporation of both [14C]acetate (P = .0001) and [3H]mevalonolactone (P = .002) into unesterified cholesterol, an effect that was markedly deficient in the hyperapoB cells (P = .0001 for [14C]acetate and P = .0002 for [3H]mevalonolactone). In normal but not hyper-apoB cells, genistein inhibited the significant stimulation by BP I of the rates of both [14C]acetate (P = .0001) and [3H]mevalonolactone (P = .04) incorporation into unesterified cholesterol.(ABSTRACT TRUNCATED AT 250 WORDS)
Kwiterovich
P O
PO
Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, Md, USA.
Motevalli
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D001055:Apolipoproteins B / Q000378:metabolism*; D016227:Benzoquinones; D002784:Cholesterol / Q000378:metabolism*; D002788:Cholesterol Esters / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D019833:Genistein; D006801:Humans; D006951:Hyperlipoproteinemias / Q000201:enzymology*; D007529:Isoflavones / Q000494:pharmacology; D047029:Lactams, Macrocyclic; D008798:Mevalonic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D009570:Nitriles / Q000494:pharmacology; D010636:Phenols / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors*; D011506:Proteins / Q000494:pharmacology*; D011809:Quinones / Q000494:pharmacology; D017828:Rifabutin / Q000031:analogs & derivatives; D014280:Triglycerides / Q000378:metabolism*; D020032:Tyrphostins
D001055:Apolipoproteins B; D016227:Benzoquinones; D002788:Cholesterol Esters; D007529:Isoflavones; D047029:Lactams, Macrocyclic; D009570:Nitriles; D010636:Phenols; D011506:Proteins; D011809:Quinones; D014280:Triglycerides; D020032:Tyrphostins; C063854:basic protein I; C060152:tyrphostin 47; D017828:Rifabutin; C015367:mevalonolactone; C020754:herbimycin; D002784:Cholesterol; D019833:Genistein; D011505:Protein-Tyrosine Kinases; D008798:Mevalonic Acid