Human soluble guanylate cyclase: functional expression and revised isoenzyme family

Area of Science:

• Biochemistry
• Molecular Biology
• Pharmacology

Background:

• Soluble guanylate cyclase (sGC) is a crucial enzyme in nitric oxide (NO) signaling, converting GTP to cGMP.
• Previous attempts to express functional human sGC subunits (alpha1-3, beta1-3) have been unsuccessful.
• Understanding human sGC is vital for developing NO-based therapeutics.

Purpose of the Study:

• To express and characterize a functionally active human heterodimeric sGC enzyme.
• To investigate the expression of sGC subunits in human tissues.
• To clarify the human sGC isoenzyme family by correcting cDNA sequencing errors.

Main Methods:

• Expression of human alpha/beta heterodimeric sGC in Sf9 insect cells.
• Enzyme activity assays using activators like sodium nitroprusside and YC-1.
• Protein detection in human tissues via Western blotting.
• Resequencing of human alpha3 and beta3 cDNA clones.

Main Results:

• Successfully expressed active recombinant human heterodimeric sGC.
• Demonstrated enzyme activation by both NO-dependent and NO-independent stimulators.
• Confirmed co-expression of alpha and beta subunits in human tissues.
• Corrected sequencing errors in human alpha3 cDNA, revealing it as the homologue of rat/bovine alpha1.

Conclusions:

• Human alpha3 and beta3 are the homologues of alpha1 and beta1, reducing the known isoenzyme family to two isoforms per subunit.
• The availability of active recombinant human sGC facilitates research into novel therapeutic compounds targeting NO signaling.