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Activity of Pyruvate Dehydrogenase A (PDHA) in Hamster Spermatozoa Correlates Positively with Hyperactivation and Is Associated with Sperm Capacitation¹

Centre for Cellular and Molecular Biology, Hyderabad 500 007, India

ABSTRACT

Unravelling the molecular basis of capacitation is crucial to our understanding the basis of acquisition of fertilization competence by spermatozoa. In two recent studies, we have demonstrated that dihydrolipoamide dehydrogenase, which is a post-pyruvate metabolic enzyme and one of the components of pyruvate dehydrogenase complex, undergoes capacitation-dependent tyrosine phosphorylation, and that the activity of the enzyme correlates with capacitation events in the hamster spermatozoa. However, it is not clear as to whether other components of the pyruvate dehydrogenase complex are also crucial for sperm capacitation. In this report, we have identified pyruvate dehydrogenase A2 (PDHA2), a constituent of pyruvate dehydrogenase A (PDHA), which is a component of pyruvate dehydrogenase complex that exhibits tyrosine phosphorylation during hamster spermatozoal capacitation. This is the first report showing that hamster sperm PDHA2 is a testis-specific phosphotyrosine that is associated with the fibrous sheath of hamster spermatozoa. The localization of PDHA2 in spermatozoa was investigated using antibodies to PDHA, which is the active tetrameric protein that consists of a homodimer of PDHA2 and PDHB. Both immunofluorescence and confocal studies indicated a unique non-canonical, extramitochondrial localization for PDHA in the principal piece of hamster spermatozoa. It was also observed that PDHA colocalized with AKAP4 in the fibrous sheath of the spermatozoon. The enzymatic activity of PDHA was positively correlated with hyperactivation but not with the acrosome reaction. Given the localization of PDHA and the evidence that its activity correlates positively with hyperactivation and that its PDHA2 subunit exhibits capacitation-associated protein tyrosine phosphorylation, it appears that PDHA2 is associated with the process of capacitation.

acrosome reaction, confocal microscopy, hamster sperm, hyperactivation, immunofluorescence, PDHA, phosphorylation, protein tyrosine, sperm, sperm capacitation

² Correspondence: Sisinthy Shivaji, Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India. FAX: 00 91 40 27160591; shivas{at}ccmb.res.in

¹ Supported by a UGC fellowship from the Government of India (to V.K.).

This article has been cited by other articles:

				V. Kumar, V. Kota, and S. Shivaji Hamster Sperm Capacitation: Role of Pyruvate Dehydrogenase A and Dihydrolipoamide Dehydrogenase Biol Reprod, August 1, 2008; 79(2): 190 - 199. [Abstract] [Full Text] [PDF]