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C J Weigel

Publications and source records attributed to C J Weigel.

6 recordsLinked to original sources
PubMed1991

Cyclic AMP-dependent protein kinase phosphorylates serine378 in vitronectin.

We previously observed that Ser378 in the heparin-binding domain of vitronectin becomes phosphorylated by a protein kinase in plasma upon addition of ATP and divalent cations. We now report that purified plasma vitronectin contains approximately 2.5 mol of phosphate per mol of protein and that vitronectin becomes phosphorylated during biosynthesis in human hepatoma (HepG2) cells. In vitro, rabbit muscle cAMP-dependent protein kinase specifically phosphorylates Ser378 in single-chain (75 kDa) vitronectin but does not phosphorylate the two-chain (65/10 kDa) form cleaved at Arg379. Heparin affects neither the time course nor the extent of phosphorylation of Ser378 at neutral pH. The extent of phosphorylation of Ser378 achieved with cAMP-dependent protein kinase (greater than or equal to 0.3 mol phosphate per mol vitronectin) is greater than that obtainable in plasma and should enable comparisons to be made of the activities of the native and phosphorylated forms.

Adenosine Triphosphate↗
PubMed1990

The presence of methionine or threonine at position 381 in vitronectin is correlated with proteolytic cleavage at arginine 379.

Vitronectin (serum spreading factor, complement S protein, epibolin) is a glycoprotein that mediates cell adhesion and interacts with components of the complement, coagulation, and fibrinolytic systems. It circulates in plasma as a 75-kDa single chain polypeptide and as a two-chain form consisting of 65- and 10-kDa polypeptides linked by a disulfide bond. An individual may have a predominance of the single chain or the two-chain form inherited as a Mendelian trait or have approximately equal amounts of both forms. Inspection of published cDNA sequences suggests that either methionine or threonine can occur at position 381, which is adjacent to the presumed site of proteolytic cleavage (Arg379-Ala380) that gives rise to the two-chain form. We have determined the presence of the Met381 and/or Thr381 alleles of the vitronectin gene in 42 individuals by oligonucleotide hybridization to genomic DNA. To determine whether this polymorphism is correlated with the susceptibility to cleavage of the Arg379-Ala380 peptide bond in vivo, we have prepared immunoblots of plasma from the same group of individuals. Nineteen individuals homozygous for the Thr381 allele had 17 +/- 9% (mean +/- S.D.) single chain vitronectin in their plasma samples. Nine individuals homozygous for the Met381 allele had 66 +/- 4% single chain vitronectin. Fourteen heterozygous individuals had 38 +/- 13% single chain vitronectin. The differences in mean values were statistically significant (p less than 0.001). These results suggest that the presence of threonine rather than methionine at position 381 of vitronectin increases the susceptibility of the protein to cleavage of the Arg379-Ala380 peptide bond in vivo.

Alleles↗