B2 AR INDUCED CAMP SIGNALING IS LOCALIZED TO THE SARCOLEMMA IN DOG HEART

B2 AR 诱导的 CAMP 信号定位于狗心脏的肌膜

• 批准号: 6097807
• 负责人: M KUSCHEL
• 金额: --
• 依托单位: NATIONAL INSTITUTE ON AGING
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6097807
• 关键词: beta adrenergic receptor; biological signal transduction; cyclic AMP; dogs; heart cell; heart contraction; muscle cells; phosphorylation; protein kinase A; protein localization; receptor expression; sarcolemma

Recent studies of b-adrenoceptor (b-AR) subtype signaling in in vitro preparations have raised doubts as to whether the cAMP/protein kinase A (PKA) signaling pathway is activated in the same manner in response to b2- AR versus b1-AR stimulation. The present study compared in the intact dog the magnitude and characteristics of chronotropic, inotropic, and lusitropic effects, the extent of cAMP accumulation, PKA activation and PKA dependent phosphorylation of key effector proteins in response to b-AR subtype stimulation. Additionally, many of these parameters and L-type Ca2+ current (ICa) were also measured in single canine ventricular myocytes. The results indicate that while the cAMP/PKA dependent phosphorylation cascade activated by b1-AR stimulation could explain the resultant modulation of cardiac function, substantial chronotropic, inotropic and lusitropic responses following b2-AR stimulation occurred in the absence of global PKA activation and phosphorylation of non-sarcolemmal proteins, including phospholamban (PLB), troponin I (Tn I), C protein and glycogen phosphorylase kinase. However, in single canine myocytes we found that the b2-AR effect to augment contraction was primarily due to augmentation of ICa, and that b2-AR-stimulated increases in both ICa and contraction were abolished by the PKA inhibitors, H-89 and Rp-cAMPS. Thus, the b2-AR-directed cAMP/PKA signaling does modulate sarcolemmal L-type Ca2+ channels, but does not regulate PKA-dependent phosphorylation of cytoplasmic proteins. These results indicate that the dissociation of b2-AR signaling from cAMP regulatory systems is only apparent, and that b2-AR-stimulated cAMP/PKA signaling is localized to subsarcolemmal space and uncoupled from phosphorylation of major non-sarcolemmal regulatory proteins involved in excitation-contraction coupling.

β-肾上腺素受体亚型的研究进展 体外制剂中的信号传导引起了人们的怀疑， cAMP/蛋白激酶A（PKA）信号通路在 对b2-AR和b1-AR刺激的反应方式相同。 本研究比较了在完整的狗， 变时性、变力性和负性效应的特征， cAMP蓄积、PKA活化和PKA依赖性 响应于b-AR的关键效应蛋白的磷酸化 亚型刺激。此外，许多这些参数和 同时测定了犬心肌细胞L型钙电流（ICa） 心室肌细胞结果表明，虽然 cAMP/PKA依赖性磷酸化级联反应 b1-AR刺激可以解释由此产生的心脏调节， 功能，实质性变时性、变力性和减力性 刺激b2-AR后的反应发生在缺乏 整体PKA激活和非肌膜磷酸化 蛋白质，包括受磷蛋白（PLB）、肌钙蛋白I（Tn I）、C 蛋白质和糖原磷酸化酶激酶。然而，在单一 我们发现，b2-AR的作用，以增加犬心肌细胞， 收缩主要是由于ICa的增加， b2-AR刺激的ICa和收缩增加， 被PKA抑制剂H-89和Rp-cAMPS消除。因此 β 2-AR介导的cAMP/PKA信号转导确实调节肌膜 L-型Ca2+通道，但不调节PKA依赖性 胞质蛋白的磷酸化。这些结果表明 b2-AR信号与cAMP调节系统的分离 仅是明显的，并且b2-AR刺激的cAMP/PKA信号传导 定位于肌膜下空间， 主要非肌膜调节蛋白的磷酸化 参与兴奋-收缩偶联。