Mutual regulatory mechanism between Ca2+ permeable receptors and channels and Ca2+ binding proteins

本研究报道了大鼠前脑Ca ~（2+）结合蛋白calbindin-D28 k（CB）和parvalbumin的表达与Ca ~（2+）渗透性AMPA受体（AMPA-Rs）的表达相关。我们使用腺病毒介导的表达系统在COS 7细胞中分析了Ca 2+不可渗透亚基GluR 2和Ca 2+可渗透亚基GluR 2 Q的细胞表面表达。使用生物素化实验的细胞表面表达的亚基的生化测量显示，细胞表面表达的GluR 2 Q与CB共表达显着增加。通过应用AMPA-R阻断剂，在CB共表达不存在的情况下，GluR 2 Q的细胞表面表达增加。为了确定Ca 2+通过Ca 2+渗透性AMPA受体进入是否引起抑制，我们使用了Ca 2+螯合剂BAPTA-AM。BAPTA-AM的应用增加了GluR 2 Q的细胞表面表达。这些结果表明，CB通过缓冲通过Ca 2+渗透性AMPA-Rs进入的增加的细胞内Ca 2+来增强Ca 2+渗透性AMPA-Rs的细胞表面表达。

We reported that the expression of Ca2+ binding proteins, calbindin-D28k (CB) and parvalbumin correlates with the expression of Ca2+ permeable AMPA receptors (AMPA-Rs) in rat forebrain. We analyzed cell surface expression of a Ca2+ impermeable subunit, GluR2 and a Ca2+ permeable subunit, GluR2Q using an adenoviral-mediated expression system in COS7 cells. Biochemical measurements of cell surface expressed subunits using biotinylation experiments revealed that cell surface expression of GluR2Q is significantly increased with CB coexpression. By application of AMPA-R blockers, cell surface expression of GluR2Q is increased in the absence of CB coexpression. To determine whether Ca2+ entry via Ca2+ permeable AMPA receptor causes the suppression, we used the Ca2+ chelater, BAPTA-AM. Application of BAPTA-AM increases cell surface expression of GluR2Q. These results suggest that CB enhances cell surface expression of Ca2+ permeable AMPA-Rs by buffering the increased intracellular Ca2+ that enters through Ca2+ permeable AMPA-Rs.