Yadav Gaya P, Annamalai Mani, Hagan D Walker, Cui Lina, Mathews Clayton, Jiang Qiu-Xing
Departments of Microbiology and Cell Science, and Medicinal Chemistry, University of Florida, Gainesville, FL 32611, USA; Departments of Materials Design and Innovation and HWI, State University of New York at Buffalo, Buffalo, NY 14201, USA; Currently at the Department of Biochemistry & Biophysics, Texas A&M University, 300 Olsen Blvd, College Station, TX 77843, USA.
Department of Pathology, College of Medicine, University of Florida, 1275 Center Drive, Gainesville, FL 32610, USA.
Int J Biol Macromol. 2025 May;309(Pt 1):142180. doi: 10.1016/j.ijbiomac.2025.142180. Epub 2025 Mar 17.
All eukaryotes utilize regulated secretion to release molecular signals packaged in secretory granules for local and remote signaling. An anion shunt conductance was first suggested in secretory granules of bovine chromaffin cells nearly five decades ago. Biochemical identity of this conductance remains undefined. CLC-3, an intracellular Cl/H exchanger, was proposed as a candidate sixteen years ago, which, however, was contested experimentally. Here, we show that chromogranin B (CHGB) makes the kernel of the long-sought anion shunter in cultured and primary neuroendocrine cells and its channel functions are essential to proper granule maturation. Intragranular pH measurements and cargo maturation assays revealed that normal granular acidification, proinsulin-insulin conversion, and dopamine-loading in neuroendocrine cells all rely on functional CHGB+ channels. Primary β-cells from Chgb-/- mice exhibited persistent granule deacidification, which suffices to uplift plasma proinsulin level, diminish glucose-induced 2nd-phase insulin secretion and dwindle monoamine content in chromaffin granules from the knockout mice. Data from targeted genetic manipulations, dominant negativity of a deletion mutant lacking channel-forming parts and tests of CLC-3/5 and ANO-1/2 all exclude CHGB-less channels from anion shunting in secretory granules. The highly conserved CHGB+ channels thus function in regulated secretory pathways in neuronal, endocrine, exocrine and stem cells of probably all vertebrates.
所有真核生物都利用调节性分泌来释放包装在分泌颗粒中的分子信号，用于局部和远程信号传递。近五十年前，人们首次在牛嗜铬细胞的分泌颗粒中发现了一种阴离子分流电导。这种电导的生化特性仍未明确。16年前，细胞内氯/氢交换体CLC-3被认为是一个候选者，但实验对此提出了质疑。在这里，我们表明嗜铬粒蛋白B（CHGB）是培养的和原代神经内分泌细胞中长期寻找的阴离子分流器的核心，其通道功能对于颗粒的正常成熟至关重要。颗粒内pH测量和货物成熟分析表明，神经内分泌细胞中的正常颗粒酸化、胰岛素原-胰岛素转化和多巴胺加载都依赖于功能性CHGB+通道。Chgb-/-小鼠的原代β细胞表现出持续的颗粒脱酸，这足以提高血浆胰岛素原水平，减少葡萄糖诱导的第二阶段胰岛素分泌，并减少敲除小鼠嗜铬颗粒中的单胺含量。来自靶向基因操作、缺乏通道形成部分的缺失突变体的显性负性以及CLC-3/5和ANO-1/2测试的数据都排除了分泌颗粒中无CHGB通道参与阴离子分流的可能性。因此，高度保守的CHGB+通道在可能所有脊椎动物的神经元、内分泌、外分泌和干细胞的调节性分泌途径中发挥作用。
