Chaudhury Arun, Cristofaro Vivian, Carew Josephine A, Goyal Raj K, Sullivan Maryrose P
Divisions of Surgery, VA Boston Healthcare System and Harvard Medical School, Boston, Massachusetts, United States of America.
Division of Urology, VA Boston Healthcare System and Harvard Medical School, Boston, Massachusetts, United States of America.
PLoS One. 2014 Feb 6;9(2):e86778. doi: 10.1371/journal.pone.0086778. eCollection 2014.
The intracellular motor protein myosin Va is involved in nitrergic neurotransmission possibly by trafficking of neuronal nitric oxide synthase (nNOS) within the nerve terminals. In this study, we examined the role of myosin Va in the stomach and penis, proto-typical smooth muscle organs in which nitric oxide (NO) mediated relaxation is critical for function. We used confocal microscopy and co-immunoprecipitation of tissue from the gastric fundus (GF) and penile corpus cavernosum (CCP) to localize myosin Va with nNOS and demonstrate their molecular interaction. We utilized in vitro mechanical studies to test whether smooth muscle relaxations during nitrergic neuromuscular neurotransmission is altered in DBA (dilute, brown, non-agouti) mice which lack functional myosin Va. Myosin Va was localized in nNOS-positive nerve terminals and was co-immunoprecipitated with nNOS in both GF and CCP. In comparison to C57BL/6J wild type (WT) mice, electrical field stimulation (EFS) of precontracted smooth muscles of GF and CCP from DBA animals showed significant impairment of nitrergic relaxation. An NO donor, Sodium nitroprusside (SNP), caused comparable levels of relaxation in smooth muscles of WT and DBA mice. These normal postjunctional responses to SNP in DBA tissues suggest that impairment of smooth muscle relaxation resulted from inhibition of NO synthesis in prejunctional nerve terminals. Our results suggest that normal physiological processes of relaxation of gastric and cavernosal smooth muscles that facilitate food accommodation and penile erection, respectively, may be disrupted under conditions of myosin Va deficiency, resulting in complications like gastroparesis and erectile dysfunction.
细胞内运动蛋白肌球蛋白Va可能通过在神经末梢内运输神经元型一氧化氮合酶（nNOS）参与一氧化氮能神经传递。在本研究中，我们研究了肌球蛋白Va在胃和阴茎中的作用，胃和阴茎是典型的平滑肌器官，其中一氧化氮（NO）介导的舒张对其功能至关重要。我们使用共聚焦显微镜和对胃底（GF）和阴茎海绵体（CCP）组织进行免疫共沉淀，以确定肌球蛋白Va与nNOS的定位并证明它们之间的分子相互作用。我们利用体外力学研究来测试在缺乏功能性肌球蛋白Va的DBA（稀释、棕色、非刺豚鼠）小鼠中，一氧化氮能神经肌肉传递过程中平滑肌舒张是否发生改变。肌球蛋白Va定位于nNOS阳性神经末梢，并在GF和CCP中与nNOS进行免疫共沉淀。与C57BL/6J野生型（WT）小鼠相比，对DBA动物的GF和CCP预收缩平滑肌进行电场刺激（EFS）显示一氧化氮能舒张明显受损。一氧化氮供体硝普钠（SNP）在WT和DBA小鼠的平滑肌中引起相当程度的舒张。DBA组织中对SNP的这些正常的接头后反应表明，平滑肌舒张受损是由于接头前神经末梢中一氧化氮合成受到抑制。我们的结果表明，分别促进食物容纳和阴茎勃起的胃和海绵体平滑肌舒张的正常生理过程，在肌球蛋白Va缺乏的情况下可能会受到干扰，从而导致诸如胃轻瘫和勃起功能障碍等并发症。
