Abstract
Sea urchin embryos swim by ciliary movement. Hypertonic shock causes deciliation and loss of motility. Within 2โ4 h, cilia regenerate and the embryos swim again. Regeneration of cilia occurs multiple times. The adenylate kinase (AK) activity of isolated cilia was studied. A 130โkDa SpโAK isozyme, present in sperm flagella, is also present in embryonic cilia. AK activity is responsible for โผ93% of nonmitochondrial ATP regeneration from ADP in embryonic cilia. This is unlike sea urchin sperm flagella, where โผ31% of the nonmitochondrial ATP regeneration is from the 130โkDa SpโAK isozyme and โผ69% from the flagellar creatine kinase (SpโCK). Embryos were deciliated 1โ3 times and after a 2โh period of regeneration the major ciliary axonemal proteins such as the tubulins appeared constant in amount. However, a moderate decrease in ATPase activity, and a large decrease of total AK activity, were measured. The decrease in AK activity paralleled the decrease in embryo swimming velocity. Embryos were deciliated once and cilia regeneration followed for 4 h. ATPase activity recovered to control levels by 3 h, but AK activity and swimming velocity remained lower than in controls. Detergent solubility data and kinetic experiments indicate that, in addition to the 130โkDa SpโAK, there is at least one additional AK isozyme in embryonic cilia. Analysis of the S. purpuratus genome indicates five AK isozymes in addition to the 130โkDa SpโAK isozyme. Decreased swimming velocity of embryos with regenerated cilia suggests that regenerated cilia are not as functionally perfect as naturally grown cilia. Cell Motil. Cytoskeleton 2007. ยฉ 2007 WileyโLiss, Inc.