β-Microseminoprotein binds CRISP-3 in human seminal plasma

Abstract

Abstractβ -Microseminoprotein (MSP) and cysteine-rich secretory protein 3 (CRISP-3) are abundant constituents of human seminal plasma. Immunoprecipitation and gel filtration of seminal plasma proteins combined with examination of the proteins in their pure form showed that MSP and CRISP-3 form stable, non-covalent complexes. CRISP-3 binds MSP with very high affinity, as evidenced by surface plasmon resonance. Due to far higher abundance of MSP in prostatic fluid, it manifests large overcapacity for CRISP-3 binding. Structural similarity with an MSP-binding protein from blood plasma suggests that CRISP-3 binds MSP through its aminoterminal SCP-domain. KeywordsCysteine-rich secretory protein; β-Microseminoprotein; PSP94; Seminal plasma; Prostate cancer; Protein complex; SCP-domain; Mass spectrometry; Surface plasmon resonance Human cysteine-rich secretory protein 3 (CRISP-3; also known as SGP28) was first isolated from neutrophilic granulocytes, but it is also a constituent of blood plasma and exocrine secretions, such as saliva and seminal plasma [1]. It belongs to a family of CRISPs found in mammals and reptiles, which is characterized by 16 highly conserved cysteine residues of a total of 220-230 amino acids and 35-85% identity in the primary structure [2][3][4]. Recently, the crystal structure of a snake venom CRISP was elucidated [5]. This confirmed the previously proposed two-domain structure of CRISPs with a large N-terminal SCP domain (after sperm coating protein, an alternative name for murine CRISP-1) and a smaller, compact C-terminal domain, separated by a hinge-region [3,5].A novel protein with an N-terminal SCP domain has been identified in human blood plasma and is called PSP94-binding protein (PSPBP) as it binds to β -microseminoprotein (MSP), also known as prostate secretory protein of 94 amino acids (PSP94) [6]. MSP is one of the three predominant proteins secreted by the prostate gland, but it is also present in other body fluids, e.g., tracheobronchial fluid. In general, MSP-synthesis is associated with tissue producing [7,8].It is yet unknown whether MSP binds to PSPBP through the SCP domain or via the large C-terminal part of the molecule [6]. One way to answer this question is to investigate whether MSP binds other proteins with an SCP domain, and the abundance of both MSP and CRISP-3 in human seminal plasma prompted us to test the hypothesis that these proteins form high-affinity complexes. Materials and methods MaterialsHuman MSP was purified from seminal plasma with the method described for the purification of pig MSP [9]. Human CRISP-3 was purified from granulocytes [10]. Specific antisera were raised in rabbits against recombinant C-terminally truncated human CRISP-3 and native human MSP [1,11]. Semen was collected from healthy volunteers and allowed to liquefy for 1 h at room temperature (RT), followed by centrifugation to remove spermatozoa and was subsequently stored at −20 °C until use. Gel filtrationProteins were separated according to their molecular size by gel filtration on a Su...

Copy number changes of CRISP3 in oral squamous cell carcinoma

“…CRISP3, which is also known as specific granule protein of 28 kDa (SGP28), belongs to a family of CRISPs characterized by their size (220-230 amino acids), their secretory properties and a content of 16 highly conserved cysteine residues, which form an intra-molecular disulphide bond (27). Apart from its ability to bind A1BG in serum, Udby et al have shown that CRISP3 forms similar complexes with one of the three major proteins secreted from the prostate in seminal plasma, β-microseminoprotein (28). Human CRISP3 is also likely to be involved in the pathogenesis of prostate cancer, where CRISP3 expression is significantly upregulated (12).…”

Effect of androgen deprivation therapy on the expression of prostate cancer biomarkers MSMB and MSMB-binding protein CRISP3

“…[16][17][18][19] We have previously reported that the cysteine-rich secretory family (CRISP) family member CRISP3 also forms a high-affinity complex with MSMB in human seminal plasma. 20 CRISP3 has been found to be one of the most upregulated genes in prostate cancer compared to benign tissue, 21,22 and was proposed to be a useful biomarker for prostate cancer. 23,24 Recently we reported that in a tissue microarray (TMA) with samples from 945 prostate cancer patients undergoing radical prostatectomy (RP), high CRISP3 and low MSMB expression were associated with poor outcome.…”

Evaluation of the prognostic significance of MSMB and CRISP3 in prostate cancer using automated image analysis

“…[22][23][24][25] In contrast with MSMB, CRISP3 (also known as specific granule protein of 28 kDa (SGP28)) levels are low in normal and benign prostatic tissue and seminal plasma, but often increased in prostate cancer, [26][27][28] in turn rendering the proposition that increasing levels of CRISP3 may be a biomarker for prostate cancer. 29 Interestingly, CRISP3 will readily form a complex with MSMB in the seminal plasma, 30 and it has been speculated that this binding may hinder any putative MSMB action. However, to date very little is known about the functions of both MSMB, CRISP3, and the complex they form.…”