Upregulation of Profilin 2 on HDAC6 overexpression in mouse GC-1 cells and its putative role in germ cell migration in the testis.

Previous reports from this laboratory have demonstrated the involvement of histone deacetylase 6 (HDAC6) in sperm motility. As the presence of HDAC6 has also been reported in the earlier stage germ cells, studies were undertaken to explore its role during these stages of spermatogenesis. HDAC6 was overexpressed in GC-1spg cells, which represent the stage between type B spermatogonia and primary spermatocyte, and its effect on germ cell transcriptome was investigated by microarray. Among the many transcripts that were differentially regulated, Profilin 2, reported previously as a neuronal specific isoform, was observed as one of the genes highly upregulated at the transcript level, which was further confirmed by real-time PCR, and the protein confirmed by indirect immunofluorescence (IIF). Profilin 2 colocalized with HDAC6, as seen both in GC-1 cells and sperm. On the sperm, the presence of Profilin 2 was detected throughout the flagella with its colocalization with HDAC6 seen conspicuously in the mid-piece region of the flagella. Co-immunoprecipitation studies confirmed Profilin 2 interaction with HDAC6. Docking studies using Z dock suggested the interaction of 8 residues of HDAC6 with 6 residues of Profilin 2. The novel observation of Profilin 2 in spermatogonial cells, its significant upregulation on HDAC6 overexpression and its interaction with HDAC6 suggests that HDAC6 in collaboration with Profilin 2 may play a role in regulating the movement of germ cells from one stage/compartment to the next.

Acetylation/deacetylation and microtubule associated proteins influence flagellar axonemal stability and sperm motility.

PTMs and microtubule-associated proteins (MAPs) are known to regulate microtubule dynamicity in somatic cells. Reported literature on modulation of α-tubulin acetyl transferase (αTAT1) and histone deacetylase 6 (HDAC6) in animal models and cell lines illustrate disparity in correlating tubulin acetylation status with stability of MT. Our earlier studies showed reduced acetyl tubulin in sperm of asthenozoospermic individuals. Our studies on rat sperm showed that on inhibition of HDAC6 activity, although tubulin acetylation increased, sperm motility was reduced. Studies were therefore undertaken to investigate the influence of tubulin acetylation/deacetylation on MT dynamicity in sperm flagella using rat and human sperm. Our data on rat sperm revealed that HDAC6 specific inhibitor Tubastatin A (T) inhibited sperm motility and neutralized the depolymerizing and motility debilitating effect of Nocodazole. The effect on polymerization was further confirmed in vitro using pure MT and recHDAC6. Also polymerized axoneme was less in sperm of asthenozoosperm compared to normozoosperm. Deacetylase activity was reduced in sperm lysates and axonemes exposed to T and N+T but not in axonemes of sperm treated similarly suggesting that HDAC6 is associated with sperm axonemes or MT. Deacetylase activity was less in asthenozoosperm. Intriguingly, the expression of MDP3 physiologically known to bind to HDAC6 and inhibit its deacetylase activity remained unchanged. However, expression of acetyl α-tubulin, HDAC6 and microtubule stabilizing protein SAXO1 was less in asthenozoosperm. These observations suggest that MAPs and threshold levels of MT acetylation/deacetylation are important for MT dynamicity in sperm and may play a role in regulating sperm motility.

In situ polyethylene sebacate particulate carriers as an alternative to Freund's adjuvant for delivery of a contraceptive peptide vaccine--A feasibility study.

The present study evaluates the feasibility of particulate carriers of a biodegradable polymer polyethylene sebacate (PES) as an alternative to Freund's adjuvant in the design of a peptide vaccine formulation. The vaccine formulation comprised of PES and the antigen KLH conjugated 80kDa HSA peptide-1 dissolved in N-methyl-2-pyrrolidone (NMP)/NMP-water as solvent. The antigen revealed good stability and the formulations were readily syringeable. Intradermal injection of the formulations resulted in the formation of PES particulates in situ at the site of injection. The NMP formulations revealed larger particulates which elicited no immunogenic response when injected in rabbits. On the other hand the NMP-water formulation revealed formation of microparticles which were significantly smaller in size, in combination with a small fraction of nanoparticles. It elicited an antibody titer up to 1:3200 in rabbits following intradermal injection. Western blot confirmed generation of antibodies specific to the peptide. Contraceptive efficacy was confirmed by loss of sperm motility and head-to-head agglutination of sperms in the treatment group. Unlike the severe reactions observed with administration of Freund's adjuvant, only mild hypersensitivity reaction was observed with the PES formulations. The mild reaction coupled with the contraceptive efficacy observed suggested PES particulates as a viable alternative to Freund's adjuvant.