Transcription of G-protein coupled receptors in corporeal smooth muscle is regulated by the endogenous neutral endopeptidase inhibitor sialorphin.
OBJECTIVE
Several reports suggest that the rat Vcsa1 gene is down-regulated in models of erectile dysfunction. The Vcsa protein product sialorphin is an endogenous neutral endopeptidase inhibitor and its down-regulation could result in prolonged activation of G-protein activated signaling pathways by their peptide agonists. We investigated whether Vcsa1 down-regulation could result in an adaptive change in GPCR (G-protein coupled receptor) expression.


METHODS
Gene expression in cultured rat corporeal smooth muscle cells following treatment with siRNA directed against Vcsa1 or the neutral endopeptidase gene was analyzed using microarray and quantitative reverse transcriptase-polymerase chain reaction. In rats Vcsa1 is one of the most down-regulated genes following bilateral transection of the cavernous nerves. In that animal model we also investigated whether Vcsa1 down-regulation was accompanied by similar changes in gene expression in corporeal smooth muscle cells in which Vcsa1 was knocked down in vitro.


RESULTS
Microarray analysis and quantitative reverse transcriptase-polymerase chain reaction demonstrated that corporeal smooth muscle cells treated in vitro with siRNA against Vcsa1 resulted in GPCR up-regulation as a functional group. In contrast, treatment of corporeal smooth muscle cells that lowered neutral endopeptidase activity resulted in decreased GPCR expression. These results suggest that the peptide product of Vcsa1, sialorphin, can effect GPCR expression by acting on neutral endopeptidase. In animals with bilaterally transected cavernous nerves the decreased Vcsa1 expression is accompanied by increased GPCR expression in cavernous tissue.


CONCLUSIONS
These experiments suggest that the mechanism by which Vcsa1 modulates erectile function is partly mediated through changes in GPCR expression.
Department of Urology and Institute of Smooth Muscle Biology, Albert Einstein College of Medicine, Bronx, New York, USA.
Yuehong
Y
Tong
Scott I
SI
Tiplitsky
Moses
M
Tar
Arnold
A
Melman
Kelvin P
KP
Davies
D000818:Animals; D002478:Cells, Cultured; D004195:Disease Models, Animal; D015536:Down-Regulation; D005786:Gene Expression Regulation / Q000187:drug effects; D008297:Male; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000502:physiology; D015260:Neprilysin / Q000037:antagonists & inhibitors*; D010410:Penile Erection / Q000187:drug effects* / Q000235:genetics* / Q000502:physiology; D011336:Probability; D011498:Protein Precursors / Q000187:drug effects / Q000378:metabolism; D011897:Random Allocation; D051381:Rats; D011916:Rats, Inbred F344; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism*; D012016:Reference Values; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012471:Salivary Proteins and Peptides / Q000187:drug effects / Q000378:metabolism / Q000494:pharmacology*; D012680:Sensitivity and Specificity
D011498:Protein Precursors; D043562:Receptors, G-Protein-Coupled; D012471:Salivary Proteins and Peptides; C066861:Smr3b protein, rat; D015260:Neprilysin