Identification of novel immunodominant epididymal sperm proteins using combinatorial approach

Abstract

Functionally immature spermatozoa leave the testis mature during epididymal transit. This process of maturation involves either addition of new proteins or modification of existing proteins onto the sperm domains that are responsible for domain-specific functions. Epididymal proteins are preferred targets for immunocontraception. In an attempt to identify epididymis-specific sperm proteins, we used a novel combinatorial approach comprising subtractive immunization (SI) followed by proteomics. Following SI, sera of mice were used for immunoproteomics, which led to the identification of 30 proteins, of which four proteins namely sperm head protein 1, sperm flagella protein 2 (SFP2), SFP3, and SFP4 are being reported for the first time on sperm. Another group of four proteins namely collagen a-2 (I) chain precursor, homeodomain-interacting protein kinase 1, GTP-binding protein Rab1, and ubiquinol cytochrome c reductase core protein II although reported earlier in testis are being reported for the first time in epididymal sperm. Furthermore, seven out of these eight novel proteins could be validated using peptide ELISA. These data are a useful repository, which could be exploited to develop targets for post-testicular immunocontraception or biomarkers for infertility diagnosis and management.

De novo sequencing and comparative analysis of testicular transcriptome from different reproductive phases in freshwater spotted snakehead Channa punctatus

“…punctatus during spawning. Among other upregulated genes of spawning phase, rgs4 , alcam and cxcl2 have been associated with gonadal stem cells [66–68] while slc6a1 and hipk1 have been reported in spermatids and spermatozoa [69,70]. Nonetheless, it is difficult to decipher the precise role of these genes in regulation of testicular events attributed to spawning phase in C .…”

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

“…Upon silver staining, the major band (∼47 kDa) of fraction III was excised from the gel and subjected to trypsin digestion for protein identification using MALDI-TOF/TOF mass spectrometry as described earlier [25]. The peptides were analyzed in MS as well as MS/MS mode to obtain sequence specific information.…”

Evaluation of Contraceptive Potential of a Novel Epididymal Sperm Protein SFP2 in a Mouse Model

“…3,4 Sperm have proteins that are sperm specific, immunogenic, and accessible to antibodies, and hence immunological intervention with these molecules can lead to infertility. 13 The identified peptide sequences of one of the novel protein, sperm flagella protein 2 (SFP2), was similar to the bullous pemphigoid antigen 1, isoform 1 ⁄ 2 ⁄ 3 ⁄ 4 [bullous pemphigoid antigen (BPA) ⁄ BPAG1 ⁄ Dystonin]. [6][7][8] However, immunization against testicular sperm proteins usually leads to orchitis, endocrine disturbance, and loss of libido.…”