Possible mechanisms underlying the biphasic regulatory effects of arachidonic acid on Ca^2 + signaling in HEK293 cells

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• 作者：Lihong Chen^a ; ¹ ; Qingli Meng^a ; ¹ ; Xinfeng Yu^a ; Chen Li^a ; Chao Zhang^a ; Chunying Cui^b ; Dali Luo^a ; ^{luodl@ccmu.edu.cn}
• 关键词：Arachidonic acid ; Ca2  ; + signal ; Membrane fluidity ; Protein kinase C
• 刊名：Cellular Signalling
• 出版年：2012
• 期刊代码：42_08986568
• 类别：bio
• 出版时间：August, 2012
• 卷：24
• 期：8
• 页码：1565-1572
• 文件大小：1305 K

摘要

Arachidonic acid (AA), an endogenous lipid signal molecule released from membrane upon cell activation, modulates intracellular Ca^2 + ([Ca^2 +]_i) signaling positively and negatively. However, the mechanisms underlying the biphasic effects of AA are rather obscure. Using probes for measurements of [Ca^2 +]_i and fluidity of plasma membrane (PM)/endoplasmic reticulum (ER), immunostaining, immunoblotting and shRNA interference approaches, we found that AA at low concentration, 3 渭M, reduced the PM fluidity by activating PKC伪 and PKC尾II translocation to PM and also the ER fluidity directly. In accordance, 3 渭M AA did not impact the basal [Ca^2 +]_i but significantly suppressed the thapsigargin-induced Ca^2 + release and Ca^2 + influx. Inhibition of PKC with G枚6983 or knockdown of PKC伪 or PKC尾 using shRNA significantly attenuated the inhibitory effects of 3 渭M AA on PM fluidity and agonist-induced Ca^2 + signal. However, AA at high concentration, 30 渭M, caused robust release and entry of Ca^2 + accompanied by a facilitated PM fluidity but decreased ER fluidity and dramatic PKC尾I and PKC尾II redistribution in the ER. Compared with ursodeoxycholate acid, a membrane stabilizing agent that only inhibited the 30 渭M AA-induced Ca^2 + influx by 45%, Gd^3 + at concentration of 10 渭M could completely abolish both release and entry of Ca^2 + induced by AA, suggesting that the potentiated PM fluidity is not the only reason for AA eliciting Ca^2 + signal. Therefore, the study herein demonstrates that a lowered PM fluidity by PKC activation and a direct ER stabilization contribute significantly for AA downregulation of [Ca^2 +]_i response, while Gd^3 +-sensitive 鈥榩ores鈥?in PM/ER play an important role in AA-induced Ca^2 + signal in HEK293 cells.