Cloning, expression, purification and functional characterization of recombinant human PSP94

MSMB variation and prostate cancer risk: clues towards a possible fungal etiology

BACKGROUND. With recent advances in high-throughput sequencing technologies, many prostate cancer risk loci have been identified, including rs10993994, a single nucleotide polymorphism (SNP) located near the MSMB gene. Variant allele (T) carriers of this SNP produce less prostate secretory protein 94 (PSP94), the protein product of MSMB, and have an increased risk of prostate cancer (approximately 25% per T allele), suggesting that PSP94 plays a protective role in prostate carcinogenesis, although the mechanisms for such protection are unclear. METHODS. We reviewed the literature on possible mechanisms for PSP94 protection for prostate cancer. RESULTS. One possible mechanism is tumor suppression, as PSP94 has been observed to inhibit cell or tumor growth in in vitro and in vivo models. Another novel mechanism, which we propose in this review article, is that PSP94 may protect against prostate cancer by preventing or limiting an intracellular fungal infection in the prostate. This mechanism is based on the recent discovery of PSP94's fungicidal activity in low-calcium environments (such as the cytosol of epithelial cells), and accumulating evidence suggesting a role for inflammation in prostate carcinogenesis. We provide further details of our proposed mechanism in this review article. CONCLUSIONS. To explore this mechanism, future studies should consider screening prostate specimens for fungi using the rapidly expanding number of molecular techniques capable of identifying infectious agents from the entire tree of life.

High-level expression, purification, characterization and structural prediction of a snake venom metalloproteinase inhibitor in Pichia pastoris

Snake venom metalloproteinase inhibitor BJ46a is from the serum of the venomous snake Bothrops jararaca. It has been proven to possess the capacity to inhibit matrix metalloproteinases (MMPs), likely based on its structural similarity to MMPs. This report describes the successful expression, purification, and characterization of the recombinant protein BJ46a in Pichia pastoris. Purified recombinant protein BJ46a was found to inhibit MMPs. Structural modeling was completed and should provide the foundation for further functional research. To our knowledge, this is the first report on the large scale expression of BJ46a, and it provides promise as a method for generation of BJ46a and investigation of its potential use as a new drug for treatment of antitumor invasion and metastasis.

Androgen dependent transcription of a mouse prostatic protein gene, PSP94: involvement of estrogen receptors

Prostatic secretory protein 94 (PSP94) is a prostatic protein found in both humans and rodents. As with other prostatic proteins, expression of this protein is regulated by androgens. In order to understand the androgen-responsive transcriptional regulation mechanisms involved, the present study aimed to identify and characterize the promoter activity of the gene. The 5'flanking (5'f) region of mouse PSP94 (mPSP94) gene was cloned and introduced into a vector upstream of the luciferase reporter gene. A Chinese hamster ovarian cell line, CHO, and a human prostate adenocarcinoma cell line, LNCaP, were transiently transfected with our reporter constructs along with an androgen receptor expression vector, and treated with dihydrotestosterone. Reporter gene assay revealed that the 5'f region of mPSP94 gene was indeed responsible for the androgen-dependent transcription. Subsequent deletion and mutation analysis indicated that the androgen responsive element (ARE)-like sequence at position -93 from the transcription start site was primarily responsible for androgen dependency. Interestingly, when estrogen receptor (ER) α was co-transfected, the androgen-dependent transcription was substantially increased. However, ERα-dependent enhancement of androgen responses was not observed when estrogen responsive element (ERE)-like motifs of the promoter region were deleted. Administration of estrogen did not influence the enhancement associated with ERα, although an anti-estrogen suppressed such effects. Collectively, these data suggest that the androgen-dependent transcription of the mPSP94 gene was co-regulated/modulated by the presence of ERα via ERE-like motifs.

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

Despite prostate cancer being the most frequent cancer in men in the Western world, tissue biomarkers for predicting disease recurrence after surgery have not been incorporated into clinical practice. Our group has previously identified β-microseminoprotein (MSMB) and cysteine-rich secretory protein-3 (CRISP3) as independent predictors of biochemical recurrence after radical prostatectomy. The purpose of the present study was to use automated image analysis, enabling quantitative determination of MSMB and CRISP3 expressions in a large cohort and to validate the previous findings. MSMB and CRISP3 protein expressions were assessed on tissue microarrays constructed from 3268 radical prostatectomy specimens. Whole-slide digital images were captured, and a novel cytoplasmic algorithm was used to develop a quantitative scoring model for cytoplasmic staining. Classification regression tree analysis was used to group patients, with different risk for biochemical recurrence, depending on level of protein expression. Patients with tumors expressing high levels of MSMB had a significantly reduced risk for biochemical recurrence after radical prostatectomy (HR=0.468; 95% CI 0.394-0.556; P<0.001). Multivariate analysis adjusted for clinicopathological parameters revealed that MSMB expression was an independent predictor of decreased risk of recurrence (HR=0.710; 95% CI 0.578-0.872; P<0.001). We found no correlation between CRISP3 expression and biochemical recurrence. In this current study, we applied a novel image analysis on a large independent cohort and successfully verified that MSMB is a strong independent factor, predicting favorable outcome after radical prostatectomy for localized prostate cancer.

Purification and preliminary X-ray crystallographic studies of beta-microseminoprotein from human seminal plasma

beta-Microseminoprotein (beta-MSP) is a small cysteine-rich protein with a molecular mass of 10 kDa. It was first isolated from human seminal plasma and has subsequently been identified from several species. Comparison of the amino-acid sequences of beta-MSP proteins suggests that the protein is a rapidly evolving protein. The function of beta-MSP is poorly understood. Furthermore, no crystal structure has been reported of any beta-MSP; therefore, determination of the crystal structure of beta-MSP is the foremost task in order to understand the function of this protein completely. Here, the purification, crystallization and preliminary X-ray diffraction analysis of beta-MSP from human seminal plasma are described. The protein was purified using anion-exchange and size-exclusion chromatography and the purified protein was crystallized using 0.1 M ammonium sulfate, 0.1 M HEPES buffer pH 7.0 and 20%(w/v) PEG 3350. The crystals belonged to the tetragonal space group P4(3)22 and contained three beta-MSP molecules in the asymmetric unit. X-ray intensity data were collected to 2.4 A resolution.