Prostate Secretory Protein of 94 Amino Acids (PSP94) Binds to Prostatic Acid Phosphatase (PAP) in Human Seminal Plasma

Abstract

Prostate Secretory Protein of 94 amino acids (PSP94) is one of the major proteins present in the human seminal plasma. Though several functions have been predicted for this protein, its exact role either in sperm function or in prostate pathophysiology has not been clearly defined. Attempts to understand the mechanism of action of PSP94 has led to the search for its probable binding partners. This has resulted in the identification of PSP94 binding proteins in plasma and seminal plasma from human. During the chromatographic separation step of proteins from human seminal plasma by reversed phase HPLC, we had observed that in addition to the main fraction of PSP94, other fractions containing higher molecular weight proteins also showed the presence of detectable amounts of PSP94. This prompted us to hypothesize that PSP94 could be present in the seminal plasma complexed with other protein/s of higher molecular weight. One such fraction containing a major protein of ∼47 kDa, on characterization by mass spectrometric analysis, was identified to be Prostatic Acid Phosphatase (PAP). The ability of PAP present in this fraction to bind to PSP94 was demonstrated by affinity chromatography. Co-immunoprecipitation experiments confirmed the presence of PSP94-PAP complex both in the fraction studied and in the fresh seminal plasma. In silico molecular modeling of the PSP94-PAP complex suggests that β-strands 1 and 6 of PSP94 appear to interact with domain 2 of PAP, while β-strands 7 and 10 with domain 1 of PAP. This is the first report which suggests that PSP94 can bind to PAP and the PAP-bound PSP94 is present in human seminal plasma.

Identification of CRISP2 from human sperm as PSP94‐binding protein and generation of CRISP2‐specific anti‐peptide antibodies

“…Interestingly, human CRISP3 and CRISP2 share 71.4% sequence identity. Earlier studies from our lab have demonstrated the ability of CRISP3 from human seminal plasma to bind to PSP94 using affinity chromatography . In this direction, we also identified CRISP2 as one of the probable binding proteins from human sperm.…”

“…Human CRISP3 is a glycosylated protein secreted mainly by the prostate and has been demonstrated to interact with prostate secretory protein of 94 amino acids (PSP94) in human seminal plasma . Previous reports have shown PSP94‐binding protein (PSPBP) from human serum to interact with PSP94 , as CRISP3 and PSPBP are only structurally related in the CAP domain.…”

Structural and molecular biology of PSP94 Its significance in prostate pathophysiology

“…Extensive studies have shown CRISP-3 to be interacting with PSP94 in human seminal plasma (122)(123)(124). Unlike PSP94, CRISP-3 expression is upregulated during prostate tumorigenesis and both have been considered for diagnosis and prognosis of PCa (88).…”

Structural analysis and characterization of new small serum proteins from the serum of a venomous snake (Gloydius blomhoffii)

“…Total RNA was prepared from 0.5 g of G. blomhoffii brevicaudus liver, using Sepasol ® -RNA I Super (Nacalai Tesque, Kyoto, Japan) according to the manufacturer's instructions, and this RNA was then reverse-transcribed to prepare the first cDNA strand by using an adaptor-linked oligo(dT) primer [5′-GGCCACGCGTCGACTAGTAC-(dT) 17 -3′]. The resulting cDNAs were further amplified by PCR by using an ssp-sigN specific primer [5′-CCCTAC-CAAGAGTTTCCTGGGTCTTCN-3′, corresponding to the 5′-untranslated region (UTR) of hSSP] and a 3′-Adp adaptor primer (5′-GGCCACGCGTCGACTAG-TAC-3′, corresponding to the adaptor sequence).…”

“…Although the biological function of PSP94 has not been unequivocally established, it has the ability to bind a protein in human blood (the PSP94-binding protein) and cysteine-rich secretory protein-3 (CRISP-3) from human leukocytes. 15,16) Anklesaria et al 17) have recently shown prostatic acid phosphatase to be another binding protein for PSP94 and proved the presence of the acid phosphatase-PSP94 complex in human seminal plasma.…”