Pituitary Center, Cedars-Sinai Medical Center, Los Angeles, California.
Research Division of Immunology, Pacific Heart Lung and Blood Institute, Los Angeles, California.
Endocrinology. 2019 Feb 1;160(2):276-291. doi: 10.1210/en.2018-00920.
Because an acidic cellular microenvironment is engendered by inflammation and may determine cell differentiation, we elucidated the impact of acidic conditions on induction of proopiomelanocortin (POMC) expression. Here, we demonstrate mechanisms for proton sensitivity of CRH receptor 1 (CRHR1) signaling to POMC and ACTH production. Low pH (6.8) resulted in doubling of POMC expression and ACTH production in pituitary cell line AtT-20 and in primary mouse pituitary cells. Using CRISPR knockout, we show that CRHR1 is necessary for acid-induced POMC expression, and this induction is mediated by CRHR1 histidine residues and calmodulin-dependent protein kinase II in both pituitary corticotroph cells and in nonpituitary cell lines expressing ectopic ACTH. In contrast, CRH ligand binding affinity to CRHR1 was decreased with acidic pH, implying that proton-induced POMC expression prevails in acidic conditions independently of CRH ligand binding. The results indicate that proton-induced CRHR1 signaling regulates ACTH production in response to an acidic microenvironment.
由于炎症会产生酸性细胞微环境，而这种环境可能会决定细胞分化，因此我们阐明了酸性条件对前阿黑皮素原（POMC）表达诱导的影响。在这里，我们展示了促肾上腺皮质激素释放激素受体 1（CRHR1）信号对 POMC 和促肾上腺皮质激素（ACTH）产生的质子敏感性的机制。低 pH 值（6.8）导致垂体细胞系 AtT-20 和原代小鼠垂体细胞中 POMC 表达和 ACTH 产生增加一倍。使用 CRISPR 敲除，我们表明 CRHR1 是酸诱导的 POMC 表达所必需的，并且这种诱导是由 CRHR1 组氨酸残基和钙调蛋白依赖性蛋白激酶 II 在垂体促肾上腺皮质细胞中和表达异位 ACTH 的非垂体细胞系中介导的。相比之下，酸性 pH 值降低了 CRH 配体与 CRHR1 的结合亲和力，这意味着质子诱导的 POMC 表达在酸性条件下独立于 CRH 配体结合而占主导地位。结果表明，质子诱导的 CRHR1 信号转导调节 ACTH 产生以响应酸性微环境。
