1996 Fiscal Year Final Research Report Summary
Pathogenesis of cerebral vasospasm, particularly phosphorylation of contractile and cytoskeletal proteins
| Project/Area Number |
06454424
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Cerebral neurosurgery
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| Research Institution | Hyogo College of Medicine |
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Principal Investigator |
TANI Eiichi Hyogo College of Medicine, Neurosurgery, Professor, 医学部, 教授 (40068424)
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| Co-Investigator(Kenkyū-buntansha) |
MINAMI Nobutaka Hyogo College of Medicine, Neurosurgery, Assistant, 医学部, 助手 (90229766)
YAMAURA Ikuya Hyogo College of Medicine, Neurosurgery, Assistant, 医学部, 助手 (50239844)
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| Project Period (FY) |
1994 – 1996
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| Keywords | vasospasm / myosin light chain / calponin / phosphorylation / protein phosphatase 1 / protein phosphatase 2A |
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| Research Abstract |
Subarachnoid hemorrhage often leads a longterm narrowing of cerebral artery called vasospasm. The present study examines two potential features of contractile system regulation in the basilar artery in vasospasm and in vasocontraction ; phosphorylation of myosin light chain (MLC) and calponin (CaP). Vasospasm was produced in the canine or rabbit basilar artery by a two-hemorrhage method. Vasocontraction was induced by local application of KCl or serotonin to the canine or rabbit basilar artery after a transclival exposure. The control animals were treated with saline instead of fresh blood. The phosphorylation of MLC was analyzed by pyrophosphate polyacrylamide gel electrophoresis (PPi PAGE), whereas that of CaP by immunoprecipitation followed by immunoblotting. Serine/threonine protein phosphatase (PP) activities were assayd with the use of [^<32>P]-labelled phosphorylase a as a substrate. The PPi PAGE showed three myosin bands in the spastic groups as well as in the KCl and serotonin
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groups, suggesting that MLC in vasospasm is phosphorylated by myosin light chain kinase (MLCK) but not by protein kinase C (PKC), because the pattern of smooth muscle myosin resolved by PPi PAGE is modified by the differential phosphorylation of MLC by MLCK and PKC ; namely, occurrence of three myosin bands in the MLCK-mediated phosphorylation and a single band in the PKC-mediated phosphorylation. In immunoprecipitation analysis, CaP was reduced in level significantly only in the spastic group. The phosphorylation of CaP on serine and threonine residues by immunoprcipitation and immunoblot analysis was increased significantly in the spastic group but not changedin the KCl and serotonin groups. Mean activities of PP1 in myofibrillar extract and PP2A in cytosolic extract were significantly decreased in the spastic group, and there was no evidence of significant changes of PP1 and PP2A in KCl and serotonin groups. Since PP1 catalyzes the dephosphorylation of MLC and CaP while PP2A catalyzes the dephosphorylation of CaP,the signisicant decrease in activities of PP1 and PP2A in vasospasm may result in continued phosphorylation of not only MLC but also CaP to increase contractility of basilar artery. In addition, the phosphorylation of CaP on tyroine residues was also significantly kincreased only in the spastic group, but its significance is unknown at present. Less
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