Adenylate Kinases 1 and 2 Are Part of the Accessory Structures in the Mouse Sperm Flagellum1

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.

Characterisation of Lyzls in mice and antibacterial properties of human LYZL6

“…However, there were not positive signals on immature spermatozoa. Mitochondrial respiration in the midpiece is a significant source of ATP required for mammalian sperm motility, 30 but only by diffusion to other regions of the tail or by active transport along the flagellum can mitochondrial ATP be used for sperm motility. However, the diffusion of ATP to the principal piece is restricted because of the long flagellum of the mammalian spermatozoa.…”

Cryopreservation of Rat Sperm

“…ATP is used by the dynein ATPases that function as the flagellar motors and in protein kinase A-mediated signal transduction pathways to regulate motility throughout the tail (Cao et al, 2006). In the mouse sperm, Mukai and Okuno (2004) reported that glycolysis has an important role in providing the ATP required for mouse sperm motility than mitochondrial respiration throughout the length of the flagellum.…”

Expression of Rat Sperm Flagellum-Movement Associated Protein Genes under 2,3,7,8-Tetrachlorodibenzo-p-dioxin Treatment

“…AK activity is necessary for ATP synthesis and to maintain an adequate concentration of ATP in eukaryotic cells. 4) It is reasonable that the expression of RGD1303144 and ODF1 is up-regulated in 7-week-old rat testis during the sexual maturation process.…”

“…Recently, AK1 and AK2 have been explored, including their expression in a maturing mouse testis. 4) These genes are expressed differentially and buffer the adenylate energy charge to produce adequate sperm motility. Taken together, an ATP energy supply and the elastic ODF protein structure are essential requirements for sperm flagellum movement.…”

“…Cao et al have reported that the expression of mouse AK1 is increased in condensing spermatids compared with pachytene spermatocytes. 4) RGD1303144 AK domain might have a different physiological function from AK1 in sperm cells, and this should now be clarified by, for example, AK activity determination of the protein.…”