1999 Fiscal Year Final Research Report Summary
CYSTEIN CONFORMATIONAL CHANGES ARE ASSOCIATED WITH INACTIVATION OF L-TYPE CALCIUM CHANNEL
| Project/Area Number |
09470012
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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 |
General physiology
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| Research Institution | Nagoya City University |
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Principal Investigator |
OBA Toshiharu NAGOYA CITY UNIVERSITY, PHYSIOLOGY, ASSOCIATE PROF., 医学部, 助教授 (50008330)
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| Co-Investigator(Kenkyū-buntansha) |
MIURA Yutaka NAGOYA CITY UNIVERSITY, BIOREG. RES., RESEARCH ASSOC., 医学部, 助手 (90285198)
HOZUMI Tetsh NAGOYA CITY UNIVERSITY, PHYSIOLOGY, RESEARCH ASSOC., 医学部, 助手 (10080102)
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| Project Period (FY) |
1997 – 1999
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| Keywords | Ca channel protein / single channel current / cysteineresidue / redox response / チャネル修飾剤 |
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| Research Abstract |
Excitation-contraction (E-C) coupling is the process whereby depolarization of the sarcolemma is translated into muscle contraction. This signal transduction process occurs at the triad junction, where the sarcoplasmic reticulum (SR) about the transverse tubule. The molecular basis of E-C coupling involves the interaction between two proteins, the SR CaィイD12+ィエD1-release channel/ryanodine receptor (RyR) and L-type CaィイD12+ィエD1 channel/DHP receptor in transverse tubules. The mechanism underlying the signal transmission from DHPR to RyR remains unknown. We have identified two classes of ryanodine receptor type 1 (RyR1) channel activity with distinct open probabilities (termed high-Po and low-Po) upon exposure to CaィイD12+ィエD1 concentrations in rabbit skeletal muscle. Effects of redox reagents and channel modulators on the high-Po channel and the low-Po channel were compared to characterize the two channels. The channel conductance and mean open time were similar between channels. Addition of DTT converted the high-Po channel to a state similar to the intact low-Po channel. The high-Po channel responded to caffeine, and adenine nucleotides. The low-Po channel was activated by an oxidant, pCMPS (p-chloro-mercuriphenylsulfonic acid), dose-dependently. The CaィイD12+ィエD1 and adenine nucleotide dependence of the oxidized low-Po channel was similar to that of the intact high-Po channel. The low-Po channel was insensitive to caffeine or adenine nucleotide, but could still response to pCMPS. These results suggest that redox states of the channel alter the response to some channel activators such as CaィイD12+ィエD1, caffeine and adenine nucleotides, as well as the channel gating.
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