Ca_V1.3 L-type channels, maxiK Ca^2 +-dependent K⁺ channels and bestrophin-1 regulate rhythmic photoreceptor outer segment phagocytosis by retinal pigment epithelial cells

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• 作者：Claudia Mü ; ller^a ; ¹ ; Né ; stor Má ; s Gó ; mez^a ; ² ; Peter Ruth^b ; Olaf Strauß ; ^a ; ³ ; ^{olaf.strauss@charite.de" class="auth_mail}
• 关键词：RPE ; retinal pigment epithelium ; POS ; photoreceptor outer segment ; MerTK ; Mer tyrosine kinase ; DHP ; dihydropyridines ; LP ; light peak ; EOG ; electro-oculogram ; SOCE ; store operated Ca2  ; + entry mechanism ; [Ca2  ; +]i ; intracellular Ca2  ; + concentration
• 刊名：Cellular Signalling
• 出版年：May, 2014
• 年：2014
• 卷：26
• 期：5
• 页码：968-978
• 全文大小：991 K

文摘

Phagocytosis of shed photoreceptor outer segments by the retinal pigment epithelium (RPE) is critical for maintenance of visual function. Because changes in intracellular Ca^2 + regulate phagocytosis, we studied in vitro the impact of different ion channels in addition to mice deficient for Ca_v1.3 L-type Ca²⁺ channels (Ca1.3^{鈭?鈭?/sup>) and maxiK Ca2+-dependent K+ channels (BK鈭?鈭?/sup>). The knockdown of Bestrophin-1 protein, a regulator of intracellular Ca2+ homeostasis, affected phagocytosis in porcine RPE cultures. Blockage of voltage-gated L-type channels by (+)BayK8644 inhibitor reduced phagocytosis in vitro, in contrast L-type activation by (鈭?BayK8644 had no impact. The expression rate of Ca_v1.3, the predominant L-type Ca2 + channel in RPE cells, varied at different times of day. Ca_V1.3鈭?鈭?/sup> RPE lacked peak phagocytic activity following morning photoreceptor shedding in wild-type RPE and retained a higher number of phagosomes at a later time of day. The BK-channel blocker paxilline lowered phagocytosis in RPE cultures in a concentration-dependent manner. BK鈭?鈭?/sup> RPE in vivo retained phagocytic capability but this activity, which is normally well synchronized with circadian photoreceptor shedding, shifted out of phase. Retinae of older BK鈭?鈭?/sup> mice showed shortened photoreceptor outer segments and diminished rhodopsin content. Store-operated Ca2 + channels Orai-1 did not affect phagocytosis in cultured RPE. TRPV channel inhibition by ruthenium-red reduced phagocytosis, whereas activation at high concentrations of 2-APB increased phagocytosis. Our data demonstrate essential roles for bestrophin-1, BK, TRPV and L-type channels in regulating retinal phagocytosis. These data indicate further the importance of BK and Ca_V1.3 for rhythmic phagocytic activity synchronized with photoreceptor shedding.}