Title: New human alpha1 soluble guanylyl cyclase splice variants as potential regulators of sGC activity
Abstract: Soluble Guanylyl Cyclase (sGC) is an obligatory heterodimeric protein (α/β), which is activated by Nitric Oxide (NO) and mediates a wide variety of NO physiological functions, including, but not restricted to vasodilation, platelet aggregation and neurotransmission. Four sGC subunits named α1, α2, β1 and β2, products of four independent genes, have been identified in humans. The α1/β1 sGC heterodimer is the main form expressed in various tissues and is regarded as the major isoform mediating vasodilation. We have identified three additional variants of α1sGC generated by alternative splicing. One α1 sGC splice form, named N1-type, codes a 363 amino acids protein with fully eliminated catalytic domain due to a 330 amino acid C-terminal deletion. This form also contains a unique stretch of 3 amino acids at the C-terminus. A second type, named N2-type, codes a protein that preserved only 126 N-terminal residues and gained additional 17 unique residues. The third identified splice α1 sGC variant, termed C-type, has a 240 amino acid deletion in the N-terminus, but maintains intact the regulatory and catalytic domains [1,2]. RT-PCR analysis of N1, N2and C-type α1 sGC mRNA levels indicates that abundance of these splice forms vary in different human tissues and during differentiation of human embryonic stem cells. These data indicate that expression of these isoforms is independently regulated.