The G-protein regulator LGN modulates the activity of the NO receptor soluble guanylate cyclase.
sGC (soluble guanylate cyclase) is the main mediator of NO signalling. Biochemical and physiological studies suggest that, besides NO, in vivo regulation of sGC involves direct interaction with other proteins. Using yeast two-hybrid screening, we identified that the multidomain LGN (Leu-Gly-Asn repeat-enriched protein) interacts with both α1 and β1 sGC subunits. LGN and sGC co-localized in the cell cytoplasm, and the LGN-sGC complex was co-immunoprecipitated from cells expressing both proteins and from native tissues. Their interaction requires the N-terminal tetratricopeptide repeats of LGN, but does not require the N-terminal portions of α1 or β1 sGC subunits. Overexpression of LGN decreases the activity of cellular sGC, whereas knockdown of LGN mRNA and protein correlated with increased sGC activity. Although purified LGN interacts directly with purified sGC, the inhibitory effect in vitro is observed only after supplementation of cell lysate to the reaction. Although resting sGC and sGC activated by the stimulator BAY41-2272 have very similar LGN-IC50 values to the NO-stimulated sGC, they have a much higher Hill coefficient, suggesting co-operative binding with respect to LGN in the low-activated state of sGC. AGS3 (activator of G-protein signalling 3), the closest LGN homologue, also inhibits sGC. The interaction of sGC with these scaffolding proteins may expand the cross-talk between NO/cGMP signalling and other cellular pathways and tailor sGC function to specific tissues or signals.
Department of Internal Medicine, Division of Cardiology, University of Texas Houston Medical School, Houston, TX 77030, USA.
Swati
S
Chauhan
Filip
F
Jelen
Iraida
I
Sharina
Emil
E
Martin
D045744:Cell Line, Tumor; D006152:Cyclic GMP / Q000378:metabolism; D006162:Guanylate Cyclase / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D000071756:Soluble Guanylyl Cyclase; D014162:Transfection
C102754:GPSM2 protein, human; D047908:Intracellular Signaling Peptides and Proteins; D021122:Protein Subunits; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D009569:Nitric Oxide; D006162:Guanylate Cyclase; D000071756:Soluble Guanylyl Cyclase; D006152:Cyclic GMP