title: Alpha1 soluble guanylyl cyclase (sGC) splice forms as potential regulators of human sGC activity.
abstract: Soluble guanylyl cyclase (sGC), a key protein in the NO/cGMP signaling pathway, is an obligatory heterodimeric protein composed of one alpha- and one beta-subunit. The alpha(1)/beta(1) sGC heterodimer is the predominant form expressed in various tissues and is regarded as the major isoform mediating NO-dependent effects such as vasodilation. We have identified three new alpha(1) sGC protein variants generated by alternative splicing. The 363 residue N1-alpha(1) sGC splice variant contains the regulatory domain, but lacks the catalytic domain. The shorter N2-alpha(1) sGC maintains 126 N-terminal residues and gains an additional 17 unique residues. The C-alpha(1) sGC variant lacks 240 N-terminal amino acids, but maintains a part of the regulatory domain and the entire catalytic domain. Q-PCR of N1-alpha(1), N2-alpha(1) sGC mRNA levels together with RT-PCR analysis for C-alpha(1) sGC demonstrated that the expression of the alpha(1) sGC splice forms vary in different human tissues indicative of tissue-specific regulation. Functional analysis of the N1-alpha(1) sGC demonstrated that this protein has a dominant-negative effect on the activity of sGC when coexpressed with the alpha(1)/beta(1) heterodimer. The C-alpha(1) sGC variant heterodimerizes with the beta(1) subunit and produces a fully functional NO- and BAY41-2272-sensitive enzyme. We also found that despite identical susceptibility to inhibition by ODQ, intracellular levels of the 54-kDa C-alpha(1) band did not change in response to ODQ treatments, while the level of 83 kDa alpha(1) band was significantly affected by ODQ. These studies suggest that modulation of the level and diversity of splice forms may represent novel mechanisms modulating the function of sGC in different human tissues.
authors.affiliation: Brown Foundation Institute of Molecular Medicine, University of Texas Houston Medical School, Houston, TX 77030, USA. iraida.g.sharina@uth.tmc.edu
authors.forename: Iraida G
authors.initials: IG
authors.lastname: Sharina
authors.forename: Filip
authors.initials: F
authors.lastname: Jelen
authors.forename: Elena P
authors.initials: EP
authors.lastname: Bogatenkova
authors.forename: Anthony
authors.initials: A
authors.lastname: Thomas
authors.forename: Emil
authors.initials: E
authors.lastname: Martin
authors.forename: Ferid
authors.initials: F
authors.lastname: Murad
mesh_terms: D017398:Alternative Splicing / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D020134:Catalytic Domain / Q000502:physiology; D045744:Cell Line, Tumor; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006162:Guanylate Cyclase / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D009928:Organ Specificity / Q000502:physiology; D010069:Oxadiazoles / Q000494:pharmacology*; D020033:Protein Isoforms / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D011810:Quinoxalines / Q000494:pharmacology*; D018160:Receptors, Cytoplasmic and Nuclear / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D000071756:Soluble Guanylyl Cyclase; D018411:Spodoptera
chemical_list: C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; D004791:Enzyme Inhibitors; D010069:Oxadiazoles; D020033:Protein Isoforms; D011810:Quinoxalines; D018160:Receptors, Cytoplasmic and Nuclear; D006162:Guanylate Cyclase; D000071756:Soluble Guanylyl Cyclase