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Phosphorylation sequences in h-caldesmon from phorbol ester-stimulated canine aortas
L P Adam1, C J Gapinski, D R Hathaway
1Department of Medicine, Indiana University School of Medicine, Indianapolis 46202.
FEBS Letters
|May 18, 1992
Summary
Vascular smooth muscle contraction involves high molecular weight caldesmon (h-caldesmon) phosphorylation. This study identifies proline-directed kinases, not protein kinase C (PKC), as responsible for h-caldesmon phosphorylation in contracting canine aortas.
Area of Science:
- Biochemistry
- Molecular Biology
- Physiology
Background:
- High molecular weight caldesmon (h-caldesmon) is phosphorylated in vascular smooth muscle.
- Phosphorylation stoichiometry increases with contractile agonist stimulation, but the kinase remains unidentified.
Purpose of the Study:
- To identify the kinase responsible for h-caldesmon phosphorylation in vascular smooth muscle.
- To compare phosphorylation sites induced by protein kinase C (PKC) in vitro with those in intact contracting tissue.
Main Methods:
- Phosphopeptides from h-caldesmon phosphorylated by PKC in vitro were sequenced.
- Phosphopeptides from h-caldesmon in PDBu-stimulated canine aortas were sequenced.
- Sequenced phosphopeptides were analyzed for kinase consensus sequences.
Main Results:
- PKC phosphorylated three C-terminal sites: GSS*LKIEE, AEFLNKS*VQK, and NLWEKQS*VDK.
- h-caldesmon from intact tissue showed phosphorylation at two C-terminal sites: VTS*PTKV and S*PAPK.
- The identified phosphorylation sites are consistent with a proline-directed protein kinase, not PKC.
Conclusions:
- h-caldesmon is directly phosphorylated by a proline-directed kinase in contracting vascular smooth muscle.
- Protein kinase C (PKC) is not the primary kinase responsible for h-caldesmon phosphorylation in this context.
- Further research is needed to identify the specific proline-directed kinase involved.