Relationship between a HCO3- -permeable conductance and a CLCA protein from rat pancreatic zymogen granules.
Relationship between a HCO3- -permeable conductance and a CLCA protein from rat pancreatic zymogen granules.
复制标题
HCO3- 通透性电导与大鼠胰腺酶原颗粒的 CLCA 蛋白之间的关系。
DOI：
10.1016/s0006-291x(02)02871-1
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发表时间：
2003
影响因子：
3.1
通讯作者：
Fuller,CatherineM
中科院分区：
文献类型：
--
作者：
Thévenod,Frank;Roussa,Eleni;Benos,DaleJ;Fuller,CatherineM
Ca 2+诱导的胰腺外分泌酶分泌尚未完全了解。我们已经提出，Ca 2+诱导的酶分泌的胰腺外分泌涉及激活的酶原颗粒（ZG）的膜中的离子电导。在这里，我们已经确定了钙激活的阴离子电导在大鼠胰腺ZG膜（ZGM）。Ca 2+（2.5-50μM）增加I-、NO3-、Br-或HCO 3-的电导，但不增加Cl-的电导，这是由缬氨霉素诱导的ZG在等渗K+盐中悬浮的渗透溶解速率确定的。4，4 ′-二异硫氰基二氢二苯乙烯-2，2 ′-二磺酸盐（100μM）或25μM二硫苏糖醇强烈抑制Ca 2+依赖性裂解。ZG阴离子电导的渗透性序列、Ca 2+依赖性和抑制剂敏感性使人想起上皮Ca 2+激活阴离子通道（CLCA）家族。用大鼠胰腺mRNA和小鼠CLCA 1引物通过RT-PCR证实CLCA表达。PCR产物（580 bp）与三种小鼠同种型mCLCA-1、mCLCA-2和mCLCA-3（mgob-5）的氨基酸相似性分别为81%、77%和57%。抗牛气管CLCA 1抗体显示CLCA表达ZGM免疫印迹，免疫过氧化物酶光学显微镜，和免疫金标记。这些发现表明，CLCA相关蛋白可以解释大鼠胰腺ZGM的Ca 2+激活的HCO 3 −电导，并有助于酶刺激的酶分泌。
Ca2+-induced enzyme secretion in the exocrine pancreas is not completely understood. We have proposed that Ca2+-induced enzyme secretion in the exocrine pancreas involves activation of ion conductances in the membrane of zymogen granules (ZG). Here we have identified a Ca2+-activated anion conductance in rat pancreatic ZG membranes (ZGM). Ca2+(2.5–50μM) increased the conductance for I−, NO3−, Br−, or HCO3−, but not for Cl−, as determined by the rate of valinomycin-induced osmotic lysis of ZG suspended in isotonic K+-salts. 4,4′-Diisothiocyanatodihydrostilbene-2,2′-disulfonate (100μM) or 25μM dithiothreitol strongly inhibited Ca2+-dependent lysis. The permeability sequence, Ca2+dependence, and inhibitor sensitivity of ZG anion conductance are reminiscent of a family of epithelial Ca2+-activated anion channels (CLCA). CLCA expression was confirmed by RT-PCR with rat pancreatic mRNA and mouse CLCA1 primers. A PCR product (580bp) exhibited 81%, 77%, and 57% amino acid similarity to the three mouse isoforms mCLCA-1, -2, and -3 (mgob-5), respectively. Antibodies against bovine tracheal CLCA1 showed CLCA expression in ZGM by immunoblotting, immunoperoxidase light microscopy, and immunogold labeling. These findings suggest that a CLCA-related protein could account for the Ca2+-activated HCO3−conductance of rat pancreatic ZGM and contribute to hormone-stimulated enzyme secretion.