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Adenylate Kinases 1 and 2 Are Part of the Accessory Structures in the Mouse Sperm Flagellum

William Penn University, Filadelfia, Pennsylvania, United States
Biology of Reproduction (Impact Factor: 3.45). 11/2006; 75(4):492-500. DOI: 10.1095/biolreprod.106.053512
Source: PubMed

ABSTRACT Proper sperm function depends on adequate ATP levels. In the mammalian flagellum, ATP is generated in the midpiece by oxidative respiration and in the principal piece by glycolysis. In locations where ATP is rapidly utilized or produced, adenylate kinases (AKs) maintain a constant adenylate energy charge by interconverting stoichiometric amounts of ATP and AMP with two ADP molecules. We previously identified adenylate kinase 1 and 2 (AK1 and AK2) by mass spectrometry as part of a mouse SDS-insoluble flagellar preparation containing the accessory structures (fibrous sheath, outer dense fibers, and mitochondrial sheath). A germ cell-specific cDNA encoding AK1 was characterized and found to contain a truncated 3' UTR and a different 5' UTR compared to the somatic Ak1 mRNA; however, it encoded an identical protein. Ak1 mRNA was upregulated during late spermiogenesis, a time when the flagellum is being assembled. AK1 was first seen in condensing spermatids and was associated with the outer microtubular doublets and outer dense fibers of sperm. This localization would allow the interconversion of ATP and ADP between the fibrous sheath where ATP is produced by glycolysis and the axonemal dynein ATPases where ATP is consumed. Ak2 mRNA was expressed at relatively low levels throughout spermatogenesis, and the protein was localized to the mitochondrial sheath in the sperm midpiece. AK1 and AK2 in the flagellar accessory structures provide a mechanism to buffer the adenylate energy charge for sperm motility.

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    • "Recently, it was demonstrated that AK1 translocates to the nucleus during cell division and associates with the mitotic spindle to provide energy for chromosome disjunction (Fig. 6.2) (Dzeja et al. 2011a). The discovery of nuclear translocation of AK1 in metaphase is in line with the adenylate kinase role in energy support of motility of cilia and flagella which have 9 + 2 microtubular structures similar to those of mitotic spindle (Cao et al. 2006; Wirschell et al. 2004). In mitotic spindles, AK1 is expected to associate with motor or anchoring proteins as it does with the Oda5 protein of the dynein complex in flagella to provide " on-site " ATP fueling capacity (van Horssen et al. 2009; Wirschell et al. 2004). "
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