Relief of autoinhibition of the electrogenic Na-HCO cotransporter NBCe1-B: role of IRBIT vs. amino-terminal truncation
Relief of autoinhibition of the electrogenic Na-HCO cotransporter NBCe1-B: role of IRBIT vs. amino-terminal truncation
复制标题
DOI：
10.1152/ajpcell.00352.2011
复制
发表时间：
2012-02-01
影响因子：
5.5
通讯作者：
Parker, Mark D.
中科院分区：
文献类型：
--
作者：
Lee, Seong-Ki;Boron, Walter F.;Parker, Mark D.
李志强，张志强，张志强。Na-HCO共转运体NBCe1-B的自抑制：IRBIT与氨基末端截断的作用。[J] .中国生物医学工程学报，2012,31(2):518- 526。首次发表于2011年10月19日；doi: 10.1152 / ajpcell.00352.2011。已知刺激电致碳酸氢钠共转运蛋白1 （NBCe1）活性的两种方法是：1)从NBCe1- c的胞质氨基端（Nt）删除包含自抑制结构域（AID）的87个氨基酸序列；2)蛋白质IRBIT与不同变体NBCe1-B中相同的87个氨基酸模块内的元件结合。理解这两种现象之间的关系将有助于了解同一NBCe1变体每次操作所引起的相对刺激强度。在本研究中，我们对表达人NBCe1-B构建体的爪蟾卵母细胞进行了双电极电压箝位，无论是否含有人IRBIT构建体。我们发现，去除AID对NBCe1-B的刺激程度与野生型IRBIT的共表达程度相同。内源性卵母细胞蛋白磷酸酶的作用明显降低了野生型IRBIT的效力：不受蛋白磷酸酶-1作用影响的突变型IRBIT对NBCe1-B的刺激程度比去除NBCe1-B AID的刺激程度高出50%。因此，IRBIT的刺激作用不能仅仅通过掩盖AID内的自身抑制决定因素来解释。最后，我们发现缺乏Nt氨基酸残基2-16的NBCe1-B结构体完全被自身抑制，但不能被IRBIT刺激，这表明胞质Nt内的自身抑制和IRBIT结合决定因素并不相同。
Lee SK, Boron WF, Parker MD. Relief of autoinhibition of the electrogenic Na-HCO cotransporter NBCe1-B: role of IRBIT vs. amino-terminal truncation. Am J Physiol Cell Physiol 302: C518-C526, 2012. First published October 19, 2011; doi: 10.1152/ajpcell.00352.2011.-Two maneuvers known to stimulate electrogenic sodium bicarbonate cotransporter 1 (NBCe1) activity are 1) deletion from the cytosolic aminoterminus (Nt) of NBCe1-C of an 87-amino acid sequence that contains an autoinhibitory domain (AID); and 2) binding of the protein IRBIT to elements within the same 87-amino acid module in a different variant, NBCe1-B. Helpful to understanding the relationship between these two phenomena would be an appreciation of the relative magnitude of stimulation caused by each maneuver for the same NBCe1 variant. In the present study, we performed two-electrode voltage-clamp on Xenopus oocytes expressing human NBCe1-B constructs, with and without human IRBIT constructs. We find that removal of the AID stimulates NBCe1-B to the same extent as coexpression of wild-type IRBIT. The potency of wild-type IRBIT apparently is reduced by the action of endogenous oocyte protein phosphatases: a mutant IRBIT that cannot be influenced by the action of protein phosphatase-1 stimulates NBCe1-B to an extent 50% greater than can be achieved by removal of the NBCe1-B AID. Thus the stimulatory effect of IRBIT cannot be explained solely by masking of autoinhibitory determinants within the AID. Finally, we find that an NBCe1-B construct that lacks amino acid residues 2-16 of the Nt is fully autoinhibited, but cannot be stimulated by IRBIT, indicating that autoinhibitory and IRBIT-binding determinants within the cytosolic Nt are not identical.