A Comparative Study of Hormonal Regulation of Three Secretory Proteins (Prostatic Secretory Protein-PSP94, Probasin, and Seminal Vesicle Secretion II) in Rat Lateral Prostate**This work was supported by an RGC Earmarked Research Grant (CUHK 4131/00M) from the Hong Kong Research Grant Council (to F.L.C.) and a grant from the Medical Research Council of Canada (to J.W.X.).

Abstract

The rat dorsolateral prostate secretes several major known proteins, although their physiological and reproductive functions are largely undefined. In the present study we examined and compared the in vivo hormonal regulation of the messenger RNA (mRNA) expression of three major secretory proteins, including prostatic secretory protein of 94 amino acids (PSP94 or beta-microseminoprotein), probasin, and seminal vesicle secretion II (SVSII), in long-term castrated lateral prostates (LP) by in situ hybridization and semiquantitative RT-PCR. The protein levels of PSP94 in the castrated LPs were also examined by Western blotting. PSP94 is a small protein newly isolated from the rat prostate gland and demonstrates highly specific expression in the LP. The results of in situ hybridization showed that PSP94, probasin, and SVSII were highly expressed in the intact LP. The hybridization signals of probasin and PSP94 disappeared in the 60-day postcastrated LPs, whereas the signals of SVSII dropped sharply in the 14-day postcastrated LPs. Similar patterns of decreasing mRNA levels of the three proteins in the castrated LPs were observed by RT-PCR analysis. Their mRNA transcripts were restored to normal levels after replacement with testosterone. The results indicate that these secretory proteins are all under androgen regulation in the rat LP. Interestingly, we also observed that their degrees of sensitivity or responsiveness to androgen withdrawal are different. Their mRNA levels dropped in response to duration of castration in the following decreasing order: SVSII, PSP94, and probasin. Besides androgen [dihydrotestosterone (DHT)], we also examined the effects of glucocorticoid [dexamethasone (DEX)], progestin [medroxyprogesterone acetate (MPA)], and zinc on their gene expressions in castrated LPs. We observed that the mRNA transcripts of both PSP94 and probasin were increased after treatments with DHT, DEX, and MPA, suggesting that these two proteins could also be regulated by glucocorticoid and progestin. In contrast with probasin, PSP94 and SVSII were not induced by ZnSO4 treatment. On the other hand, SVSII expression was only increased significantly by DHT and moderately by MPA, but not by DEX, suggesting that SVSII is under strict control by androgen.

Increased prostate cell proliferation and loss of cell differentiation in mice lacking prostate epithelial androgen receptor

“…Probasin, Nkx3.1, and prostatic secretory protein-94 (PSP94) are three prostate-specific proteins known to be transcriptionally regulated by androgens (16,17). However, it is unknown whether stromal AR or epithelial AR is responsible for their expression.…”

Prostate-specific markers to identify rare prostate cancer cells in liquid biopsies

“…Prostate secretory protein of 94 amino acids (PSP94, gene name MSMB ) is one of the first three secretory proteins in the prostate to be identified, in addition to PSA and PSAP 203 . PSP94 was originally identified as beta-microseminoprotein (MSMB) 204 , or beta-inhibin 205 , and is an androgen-regulated immunoglobulin-binding factor that is secreted into seminal plasma 206–209 . Its specific function is still uncertain, but it has been suggested that it increases sperm quality 210 and acts as a fungicidal agent in sperm 211 .…”