Dagnino-Acosta Adan, Guerrero-Hernandez Agustín
Centro Universitario de Investigaciones Biomédicas, CONACYT-Universidad de Colima, Colima, Mexico.
Departamento de Bioquímica, Centro de Investigación y de Estudios Avanzados, Mexico City, Mexico.
Front Physiol. 2022 Jun 28;13:925023. doi: 10.3389/fphys.2022.925023. eCollection 2022.
PKC inhibitors stimulate Ca release from internal stores in diverse cell types. Our data indicate that this action cannot be explained by an increased agonist-induced IP production or an overloaded SR Ca pool in smooth muscle cells from guinea pig urinary bladder. The incubation of these cells with three different PKC inhibitors, such as Go6976, Go6983, and BIM 1, resulted in a higher SR Ca leak revealed by inhibition of the SERCA pump with thapsigargin. This SR Ca leakage was sensitive to protein translocation inhibitors such as emetine and anisomycin. Since this increased SR Ca leak did not result in a depleted SR Ca store, we have inferred there was a compensatory increase in SERCA pump activity, resulting in a higher steady-state. This new steady-state increased the frequency of Spontaneous Transient Outward Currents (STOCs), which reflect the activation of high conductance, Ca-sensitive potassium channels in response to RyR-mediated Ca sparks. This increased STOC frequency triggered by PKC inhibition was restored to normal by inhibiting translocon-mediated Ca leak with emetine. These results suggest a critical role of PKC-mediated translocon phosphorylation in regulating SR Ca steady-state, which, in turn, alters SR Ca releasing activity.
蛋白激酶C（PKC）抑制剂可刺激多种细胞类型从内部储存库释放钙离子。我们的数据表明，在豚鼠膀胱平滑肌细胞中，这种作用无法通过激动剂诱导的肌醇磷酸（IP）生成增加或肌浆网（SR）钙池过载来解释。用三种不同的PKC抑制剂（如Go6976、Go6983和BIM 1）孵育这些细胞，会导致在用毒胡萝卜素抑制肌浆网钙ATP酶（SERCA）泵后，显示出更高的肌浆网钙泄漏。这种肌浆网钙泄漏对蛋白质转运抑制剂（如依米丁和茴香霉素）敏感。由于这种增加的肌浆网钙泄漏并未导致肌浆网钙储存耗尽，我们推断SERCA泵活性有代偿性增加，从而导致更高的稳态。这种新的稳态增加了自发瞬态外向电流（STOCs）的频率，STOCs反映了高电导、钙敏感钾通道在响应兰尼碱受体（RyR）介导的钙火花时的激活。通过用依米丁抑制转位子介导的钙泄漏，PKC抑制引发的这种增加的STOC频率恢复正常。这些结果表明，PKC介导的转位子磷酸化在调节肌浆网钙稳态中起关键作用，进而改变肌浆网钙释放活性。
