Functional Characterization of Two Distinct Transcripts Encoding the Membrane or Soluble Forms of Guanylyl Cyclase-G

• Main Authors: Pei-Yi Tsai, 蔡佩宜
• Other Authors: Ruey-Bing Yang
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/01008803031910957093

碩士 === 國立陽明大學 === 藥理學研究所 === 96 === Intracellular second-messenger cGMP is involved in the regulation of a broad spectrum of physiological functions, including relaxation of vascular smooth muscle, repression of platelets coagulation, and electrolytes homeostasis. In the mammal, cGMP is synthesized by two major classes of enzymes: the soluble and the membrane-associated receptor guanylyl cyclases (GCs). To date, seven isoforms of receptor GCs have been described in mammals, termed GC-A to GC-G in the order of their discovery. We recently identified receptor GC-G from mouse testis. However, the expression of different GC-G transcripts and the regulation of their encoded products are largely unknown. To facilitate the functional studies, we first generate a dominant-negative (DN) mutant of receptor GC-G by introduction of an alanine (D950A) at a well-conserved Asp-950 critical for the GC activity. When overexpressed, the GC-G-D950A mutant resulted in an inactive cyclase that could form a complex and suppress a greater than 50% production of overall cGMP by the GC-G-WT protein. Therefore, this DN mutant will serve as a valuable tool to further dissect the function of cGMP signaling mediated by receptor GC-G. In addition, a shorter transcript encoding a new type of soluble GC-G, designated as kinase-like domain containing soluble GC-G (ksGC-G), was found in a wide range of tissues. Most interestingly, the ksGC-G activity could interact with nitric oxide (NO)-regulated sGC subunits, which has been implied in a variety of biological processes. Together, our results demonstrated, for the first time, that GC-G is a multi-functional protein through action by at least two distinct transcripts.