Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA.
Department of Pharmacology, University of California San Diego, La Jolla, California, USA.
Acta Physiol (Oxf). 2024 Oct;240(10):e14205. doi: 10.1111/apha.14205. Epub 2024 Jul 19.
To identify the physiological role of the acid-base sensing enzyme, soluble adenylyl cyclase (sAC), in red blood cells (RBC) of the model teleost fish, rainbow trout.
We used: (i) super-resolution microscopy to determine the subcellular location of sAC protein; (ii) live-cell imaging of RBC intracellular pH (pH) with specific sAC inhibition (KH7 or LRE1) to determine its role in cellular acid-base regulation; (iii) spectrophotometric measurements of haemoglobin-oxygen (Hb-O) binding in steady-state conditions; and (iv) during simulated arterial-venous transit, to determine the role of sAC in systemic O transport.
Distinct pools of sAC protein were detected in the RBC cytoplasm, at the plasma membrane and within the nucleus. Inhibition of sAC decreased the setpoint for RBC pH regulation by ~0.25 pH units compared to controls, and slowed the rates of RBC pH recovery after an acid-base disturbance. RBC pH recovery was entirely through the anion exchanger (AE) that was in part regulated by HCO -dependent sAC signaling. Inhibition of sAC decreased Hb-O affinity during a respiratory acidosis compared to controls and reduced the cooperativity of O binding. During in vitro simulations of arterial-venous transit, sAC inhibition decreased the amount of O that is unloaded by ~11%.
sAC represents a novel acid-base sensor in the RBCs of rainbow trout, where it participates in the modulation of RBC pH and blood O transport though the regulation of AE activity. If substantiated in other species, these findings may have broad implications for our understanding of cardiovascular physiology in vertebrates.
鉴定酸碱感应酶可溶性腺苷酸环化酶（sAC）在模式硬骨鱼虹鳟红细胞（RBC）中的生理作用。
我们使用：（i）超分辨率显微镜确定 sAC 蛋白的亚细胞位置；（ii）用特异性 sAC 抑制物（KH7 或 LRE1）对 RBC 细胞内 pH（pH）进行活细胞成像，以确定其在细胞酸碱调节中的作用；（iii）在稳态条件下用分光光度法测量血红蛋白-氧（Hb-O）结合；以及（iv）在模拟动静脉转运期间，确定 sAC 在全身 O 转运中的作用。
在 RBC 细胞质、质膜和核内检测到明显的 sAC 蛋白库。与对照相比，sAC 抑制将 RBC pH 调节的设定点降低了约 0.25 pH 单位，并且减缓了酸碱扰动后 RBC pH 恢复的速率。RBC pH 的恢复完全通过阴离子交换器（AE）进行，部分受到 HCO3-依赖性 sAC 信号的调节。与对照相比，sAC 抑制降低了呼吸性酸中毒期间 Hb-O 的亲和力，并降低了 O 结合的协同性。在动静脉转运的体外模拟中，sAC 抑制使~11%的 O 释放量减少。
sAC 是虹鳟 RBC 中的一种新型酸碱传感器，通过调节 AE 活性参与 RBC pH 和血液 O 转运的调节。如果在其他物种中得到证实，这些发现可能对我们理解脊椎动物心血管生理学具有广泛的意义。
