Adenylate kinase in sea urchin embryonic cilia

Abstract

Sea urchin embryos swim by ciliary movement. Hypertonic shock causes deciliation and loss of motility. Within 2-4 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 130-kDa Sp-AK isozyme, present in sperm flagella, is also present in embryonic cilia. AK activity is responsible for approximately 93% of nonmitochondrial ATP regeneration from ADP in embryonic cilia. This is unlike sea urchin sperm flagella, where approximately 31% of the nonmitochondrial ATP regeneration is from the 130-kDa Sp-AK isozyme and approximately 69% from the flagellar creatine kinase (Sp-CK). Embryos were deciliated 1-3 times and after a 2-h 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 130-kDa Sp-AK, 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 130-kDa Sp-AK isozyme. Decreased swimming velocity of embryos with regenerated cilia suggests that regenerated cilia are not as functionally perfect as naturally grown cilia.

Role of Adenylate Kinase Type 7 Expression on Cilia Motility: Possible Link in Primary Ciliary Dyskinesia

“…Several AKs are located in cilia and flagella, tightly associated with axonemes, providing ATP that is hydrolyzed by axonemal dynein ATPase to support axonemal bending waves. 5 Furthermore, AK7 is a multidomain protein highly conserved only in organisms possessing motile (9 ϩ 2) cilia.…”

“…4 Members of the adenylate kinase (AK) family, responsible for 2ADP 7 ATP ϩ AMP regeneration, have been implicated in ciliary function and homeostasis. 5,6 In particular, AK type 7 (AK7) is highly expressed in ciliated human bronchial epithelium, 7 and according to recent data reported by Fernandez-Gonzalez et al, 8 the mutant AK7 Ϫ/Ϫ mouse presents with ultrastructural ciliary defects and low ciliary beat frequency (CBF). However, the contribution of AK7 ex-pression and its genetic integrity on human cilia function is largely unknown.…”

Evolutionary origins of the purinergic signalling system

“…2007). ATP also appears to be involved in the activities of cilia in sea urchin embryos (Kinukawa & Vacquier 2007). Ecto‐ATP diphosphohydrolase (apyrase) is present in ovarian follicle cells of the starfish Asterina pectinifera (Mita et al.…”

Evolution of P2X receptors

“…Regulation of on/off switching of dynein motile activity of the flagella of sea urchin sperm has been shown to involve ADP‐induced activation and ATP‐induced inhibition, probably through phosphorylation/dephosphorylation of outer arm‐linked proteins 79. ATP also appears to be involved in the activities of cilia in sea urchin embryos 80. Control of luminescence in the brittlestar, Amphipholis squamata , may involve P2X‐like receptors acting in synergy with acetylcholine 81…”