Institute of Experimental Biomedicine, University Hospital Würzburg, 97080 Würzburg, Germany.
Leibniz-Institut für Analytische Wissenschaften (ISAS), 44139 Dortmund, Germany.
Int J Mol Sci. 2022 Jan 27;23(3):1469. doi: 10.3390/ijms23031469.
Cyclophilin A (CyPA) is widely expressed by all prokaryotic and eukaryotic cells. Upon activation, CyPA can be released into the extracellular space to engage in a variety of functions, such as interaction with the CD147 receptor, that contribute to the pathogenesis of cardiovascular diseases. CyPA was recently found to undergo acetylation at K82 and K125, two lysine residues conserved in most species, and these modifications are required for secretion of CyPA in response to cell activation in vascular smooth muscle cells. Herein we addressed whether acetylation at these sites is also required for the release of CyPA from platelets based on the potential for local delivery of CyPA that may exacerbate cardiovascular disease events. Western blot analyses confirmed the presence of CyPA in human and mouse platelets. Thrombin stimulation resulted in CyPA release from platelets; however, no acetylation was observed-neither in cell lysates nor in supernatants of both untreated and activated platelets, nor after immunoprecipitation of CyPA from platelets. Shotgun proteomics detected two CyPA peptide precursors in the recombinant protein, acetylated at K28, but again, no acetylation was found in CyPA derived from resting or stimulated platelets. Our findings suggest that acetylation of CyPA is not a major protein modification in platelets and that CyPA acetylation is not required for its secretion from platelets.
亲环素 A（CyPA）广泛存在于所有原核和真核细胞中。在激活后，CyPA 可以被释放到细胞外空间，从而发挥各种功能，如与 CD147 受体相互作用，这有助于心血管疾病的发病机制。最近发现 CyPA 在 K82 和 K125 两个赖氨酸残基处发生乙酰化，这两个赖氨酸残基在大多数物种中都保守，这些修饰对于血管平滑肌细胞激活时 CyPA 的分泌是必需的。在此，我们基于 CyPA 可能局部递送来加重心血管疾病事件的潜力，研究了这些位点的乙酰化是否也是从血小板中释放 CyPA 所必需的。Western blot 分析证实了人类和小鼠血小板中存在 CyPA。凝血酶刺激导致血小板释放 CyPA；然而，无论是在细胞裂解物中还是在未处理和激活的血小板上清液中，也无论是在从血小板中免疫沉淀 CyPA 后，都没有观察到乙酰化 - 既没有在细胞裂解物中，也没有在血小板上清液中。鸟枪法蛋白质组学检测到重组蛋白中的两个 CyPA 肽前体在 K28 处乙酰化，但再次发现，来自静止或刺激的血小板的 CyPA 中没有发现乙酰化。我们的研究结果表明，CyPA 的乙酰化不是血小板中的主要蛋白质修饰，并且 CyPA 的乙酰化不是其从血小板中分泌所必需的。
