MOLECULAR MECHANISM FOR ERECTILE FUNCTION & DYSFUNCTION

勃起（肿胀）是一种复杂的神经生理事件， 海绵体平滑肌细胞松弛 阴茎允许血液填充到海绵体空间， 阴茎的大小和硬度增加。 痿 （detumescence）是通过收缩 阴茎海绵体平滑肌细胞。 CCSM是独一无二的 因为它大部分时间保持在收缩状态。 不 知道Ca 2 +-钙调素-MLCK通路或其他然后丝- 介导的调节（通过肌动蛋白结合蛋白caldesmon）发挥作用， 作用是保持这些细胞处于收缩状态，以便阴茎 保持软弱。 第三种可能性是， CCSM在确定力产生的速度方面发挥作用， 紧张度 该研究人员最近进行的一项研究表明， 平滑肌被认为是紧张性的，含有一种肌球蛋白 而小肌肉动脉中的平滑肌细胞 含有不同的肌球蛋白同种型。 后一种亚型由以下编码 一种肌球蛋白重链mRNA，其被选择性剪接以插入一个 21-编码ATP结合位点附近区域的核苷酸序列 肌球蛋白头部的部位。 该插入片段编码一个7-氨基酸肽， 并且所产生的肌球蛋白同种型具有两倍的增加， 肌动蛋白激活的肌球蛋白ATP酶活性和相关的 缩短速度（Vmax）。 我们在CCSM上进行的类似研究 实验室表明，CCSM包含插入（如在小肌肉 动脉和所有内脏平滑肌， 特征）和非插入（如在主动脉平滑肌中， 肌球蛋白重链同种型。 特别地，使用来自正常兔、正常人和正常人的CCSM， 勃起功能障碍患者，我们将解决以下问题 问题：（1）收缩特性的差异 CCSM与其他来源的平滑肌相比， 平滑肌肌球蛋白亚型组成的差异， 是由肌球蛋白前体mRNA在3'端的选择性剪接产生的。 末端（导致SM 1和SM 2）或5'末端（导致插入的SM 2）。 肌球蛋白）？ (2)肌球蛋白轻链磷酸化起什么作用 在勃起功能中，CCSM细胞是否具有较高的激酶或较低的 磷酸酶活性与其他平滑肌细胞（例如， 膀胱平滑肌）？ (3)什么是表达水平 肌球蛋白轻链激酶和钙调蛋白在CCSM中的作用， 勃起功能障碍的患者吗 因此，结果从 本申请中提出的实验将提供分子 调节CCSM收缩的机制，并描绘 过桥自行车的具体步骤， 正常人体平滑肌细胞的收缩性 阴茎海绵体 它还将提供和解释的变化 平滑肌细胞的收缩性， 勃起功能障碍

Erection(tumescence) is a complex neurophysiologic event that leads to relaxation of the smooth muscle cells in the corpus cavernosum penis which allows filling of blood into the cavernous spaces causing an increase in the size and rigidity of the penis. Flaccidity (detumescence) is initiated and maintained by contraction of the corpus cavernosum smooth muscle (CCSM) cells. The CCSM is unique since it remains in the contracted state most of the time. It is not know whether the Ca2+-calmodulin-MLCK pathway or other then filament- mediated regulation (via the actin-binding protein caldesmon) plays a role in keeping these cells in the contracted state, for the penis to remain flaccid. A third possibility is that the myosin isoforms in CCSM play a role in determining the velocity of force generation and the tonicity. A recent study conducted by this investigator showed that the aortic smooth muscle, which is considered tonic, contains one type of myosin isoform whereas the smooth muscle cells in small muscular arteries contain a different myosin isoform. The latter isoform is encoded by a myosin heavy chain mRNA that is alternatively spliced to insert a 21-nucleotide sequence that encodes a region near the ATP-binding site on the myosin head. This insert encodes a 7-amino acid peptide, and the resulting myosin isoform has a two-fold increase in the actin-activated myosin ATPase activity and an associated increase in shortening velocity (Vmax). Similar studies conducted on CCSM in our lab show that the CCSM contains both inserted (as in small muscular arteries and all visceral smooth muscles which show phasic characteristics) and non-inserted (as in aortic smooth muscle which is tonic) myosin heavy chain isoforms. Specially, using CCSM from normal rabbits, normal humans, and patients with erectile dysfunctions, we will address the following questions: (1) Are the differences in the contractile characteristics of CCSM compared to smooth muscle from other sources due to a difference in the composition of smooth muscle myosin isoforms that are produced by alternative splicing of the myosin pre-mRNA at the 3' end (resulting in SM1 and SM2) or the 5' end (resulting in inserted myosin)? (2) What role does myosin light chain phosphorylation play in erectile function and do CCSM cells have higher kinase or lower phosphatase activity compared to other smooth muscle cells (e.g. bladder smooth muscle)? (3) What is the level of expression of myosin light chain kinase and caldesmon in the CCSM and is it altered in patients with erectile dysfunction? Thus, the results from experiments proposed in this application will provide the molecular mechanisms for the regulation of CCSM contraction and delineate specific steps in the pathways for cross-bridge cycling and contractility of smooth muscle cells in the normal corporus cavernosum penis. It will also provide and explanation for changes in contractility of smooth muscle cells seen in patients with erectile dysfunction.