Department of Anatomy (Cell Biology), Iwate Medical University, 2-1-1 Nishitokuda, Yahaba, Iwate, 028-3694, Japan.
Histochem Cell Biol. 2013 Oct;140(4):463-76. doi: 10.1007/s00418-013-1082-0. Epub 2013 Mar 6.
Protease-activated receptors (PARs) represent a novel class of seven transmembrane domain G-protein coupled receptors, which are activated by proteolytic cleavage. PARs are present in a variety of cells and have been prominently implicated in the regulation of a number of vital functions. Here, lacrimal gland acinar cell responses to PAR activation were examined, with special reference to intracellular Ca(2+) concentration ([Ca(2+)]i) dynamics. In the present study, detection of acinar cell mRNA specific to known PAR subtypes was determined by reverse transcriptase polymerase chain reaction. Only PAR2 mRNA was detected in acinar cells of lacrimal glands. Both trypsin and a PAR2-activating peptide (PAR2-AP), SLIGRL-NH2, induced an increase in [Ca(2+)]i in acinar cells. The removal of extracellular Ca(2+) and the use of Ca(2+) channel blockers did not inhibit PAR2-AP-induced [Ca(2+)]i increases. Furthermore, U73122 and xestospongin C failed to inhibit PAR2-induced increases in [Ca(2+)]i. The origin of the calcium influx observed after activated PAR2-induced Ca(2+) release from intracellular Ca(2+) stores was also evaluated. The NO donor, GEA 3162, mimicked the effects of PAR2 in activating non-capacitative calcium entry (NCCE). However, both calyculin A (100 nM) and a low concentration of Gd(3+) (5 μM) did not completely block the PAR2-AP-induced increase in [Ca(2+)]i. These findings indicated that PAR2 activation resulted primarily in Ca(2+) mobilization from intracellular Ca(2+) stores and that PAR2-mediated [Ca(2+)]i changes were mainly independent of IP3. RT-PCR indicated that TRPC 1, 3 and 6, which play a role in CCE and NCCE, are expressed in acinar cells. We suggest that PAR2-AP differentially regulates both NCCE and CCE, predominantly NCCE. Finally, our results suggested that PAR2 may function as a key receptor in calcium-related cell homeostasis under pathophysiological conditions such as tissue injury or inflammation.
蛋白酶激活受体（PARs）是一类新型的七跨膜结构域 G 蛋白偶联受体，它们通过蛋白水解切割而被激活。PARs 存在于多种细胞中，并被广泛认为参与了许多重要功能的调节。在这里，我们研究了 PAR 激活对泪腺腺泡细胞的反应，特别关注细胞内 Ca(2+)浓度 ([Ca(2+)]i) 动力学。在本研究中，通过逆转录聚合酶链反应检测了已知 PAR 亚型在腺泡细胞中的 mRNA 特异性。仅在泪腺腺泡细胞中检测到 PAR2 mRNA。胰蛋白酶和 PAR2 激活肽 (PAR2-AP) SLIGRL-NH2 均可诱导腺泡细胞 [Ca(2+)]i 增加。去除细胞外 Ca(2+) 和使用 Ca(2+) 通道阻滞剂并不能抑制 PAR2-AP 诱导的 [Ca(2+)]i 增加。此外，U73122 和 xestospongin C 未能抑制 PAR2 诱导的 [Ca(2+)]i 增加。还评估了 PAR2 诱导细胞内 Ca(2+) 释放后观察到的钙内流的起源。NO 供体 GEA 3162 模拟了 PAR2 激活非电容性钙内流 (NCCE) 的作用。然而，calyculin A（100 nM）和低浓度 Gd(3+)（5 μM）均不能完全阻断 PAR2-AP 诱导的 [Ca(2+)]i 增加。这些发现表明，PAR2 激活主要导致细胞内 Ca(2+) 库中的 Ca(2+) 动员，并且 PAR2 介导的 [Ca(2+)]i 变化主要独立于 IP3。RT-PCR 表明，在 CCE 和 NCCE 中起作用的 TRPC 1、3 和 6 在腺泡细胞中表达。我们认为，PAR2-AP 差异调节 NCCE 和 CCE，主要是 NCCE。最后，我们的结果表明，PAR2 可能在组织损伤或炎症等病理生理条件下作为钙相关细胞内稳态的关键受体发挥作用。
