Cav1.1
Cav1.1又稱為L型鈣通道α1亞基(calcium channel, voltage-dependent, L type, alpha 1S subunit,CACNA1S),為一種由CACNA1S基因轉譯而成的蛋白質[7]。有時又稱CACNL1A3或二氫吡啶受體(dihydropyridine receptor,DHPR)。
功能
該蛋白為骨骼肌中L型電性鈣通道的五個次單元中的其中之一。該基因突變可能與低鉀血周期性麻痺、甲狀腺毒性週期性麻痺症,和惡性高熱相關[7]。
Cav1.1為骨骼肌橫小管上的電壓依賴性鈣通道。在骨骼肌中會與肌漿網上的蘭諾定受體1(RyR1)相接。當神經衝動發生時,終板電位會沿骨骼肌的細胞膜傳入橫小管中,並刺激Cav1.1。先前科學家以為當肌肉去極化時會引發鈣通道開啟,鈣離子流入後活化RyR1,使更多鈣離子從肌漿網釋入細胞質,引發興奮收縮聯合作用,進而使肌肉收縮。最近研究發現在骨骼肌中(並非心肌),鈣離子流入Cav1.1並非必須。Cav1.1活化後構型會改變,並與RyR1相接進行別構調節[8]。
臨床意義
在許多低鉀血周期性麻痺(HOKPP)患者身上,Cav1.1的 domains 2 和 domains 4 有突變發生,造成其感測去極化的能力下降,活化蘭諾定受體的能力下降。因此肌肉無法順利收縮,導致患者癱瘓。此類患者會於低血鉀時發生癱瘓,因胞外血鉀降低會使肌肉更快回到靜息電位,且會使電位更難達到閾值,使動作電位更難產生,肌肉因此無力。在Cav1.1缺損的患者身上,即使動作電位產生,肌漿網仍難以釋放鈣離子,使肌肉收縮無法完成,因此此類患者必須調整血鉀濃度。相反地,若鈉離子通道突變後功能增強,使肌肉長期維持去極化,則會導致高鉀血周期性麻痺[9]。
歐洲惡性高熱小組(European Malignant Hyperthermia Group)將此 CACNA1S 基因的兩種突變列為惡性高熱的診斷之一[10]。
阻斷劑
Cav1.1可由二羥基吡啶阻斷。
參見
參考文獻
- ^ 與Cav1.1相關的疾病;在維基數據上查看/編輯參考.
- ^ 對Cav1.1起作用的藥物;在維基數據上查看/編輯參考.
- ^ 3.0 3.1 3.2 GRCh38: Ensembl release 89: ENSG00000081248 - Ensembl, May 2017
- ^ 4.0 4.1 4.2 GRCm38: Ensembl release 89: ENSMUSG00000026407 - Ensembl, May 2017
- ^ Human PubMed Reference:. National Center for Biotechnology Information, U.S. National Library of Medicine.
- ^ Mouse PubMed Reference:. National Center for Biotechnology Information, U.S. National Library of Medicine.
- ^ 7.0 7.1 Entrez Gene: CACNA1S calcium channel, voltage-dependent, L type, alpha 1S subunit. (原始內容存檔於2010-12-05).
- ^ Proenza C, O'Brien J, Nakai J, Mukherjee S, Allen PD, Beam KG. Identification of a region of RyR1 that participates in allosteric coupling with the alpha(1S) (Ca(V)1.1) II-III loop. J. Biol. Chem. February 2002, 277 (8): 6530–5. PMID 11726651. doi:10.1074/jbc.M106471200.
- ^ Jurkat-Rott K, Lehmann-Horn F. Muscle channelopathies and critical points in functional and genetic studies. J. Clin. Invest. August 2005, 115 (8): 2000–9. PMC 1180551 . PMID 16075040. doi:10.1172/JCI25525.
- ^ European Malignant Hyperthermia Group: Mutations in RYR1. emhg.org. [2017-07-07]. (原始內容存檔於2016-03-21) (英語).
延伸閱讀
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