Activation of sea-urchin sperm motility is accompanied by an increase in the creatine kinase exchange flux

Abstract

The kinetics of the creatine kinase (CK) reaction were studied in suspensions of quiescent and active, intact sea-urchin spermatozoa in artificial seawater, using 31P-NMR magnetization transfer. In inactive sperm, no CK-mediated exchange flux was detected, whereas in activated motile sperm, the forward pseudo-first-order rate constant was 0.13±0.04 s-1 at 10 °C, corresponding to a steady-state CK flux of 3.1±0.5 mM·s-1. Intracellular pH shifted from 6.6±0.1 to 7.6±0.1 upon activation. The phosphocreatine (PCr)/ATP and PCr/Pi ratios were only marginally reduced in activated sperm, whereas the estimated cytosolic free ADP concentration increased remarkably from 9 μM in quiescent, to 114 μM in activated spermatozoa. The elevation of CK flux upon sperm activation is discussed in the light of the proposition that in sea-urchin spermatozoa, which are fuelled entirely by oxidative phosphorylation, high-energy phosphate transport is mediated by a ‘CK/PCr shuttle‘.

Does intracellular metabolite diffusion limit post-contractile recovery in burst locomotor muscle?

“…These are likely to include systems with relatively high rates of ATP production/consumption and distant sites of ATP utilization, such as in some muscle fibers with a higher aerobic capacity than examined here (Meyer et al, 1984;Stokes and Josephson, 1992;Vendelin et al, 2000;Saks et al, 2003;Suarez, 2003) or in the flagellum of spermatozoa, which has been the subject of many reaction-diffusion analyses (e.g. Nevo and Rikmenspoel, 1969;Tombes and Shapiro, 1985;Van Dorsten et al, 1997;Ellington and Kinsey, 1998). However, it is possible that in most cases neither intracellular metabolite diffusion nor sarcolemmal O 2 flux limit aerobic metabolism per se, but even if this is true it is still likely that the interaction between diffusive processes and ATP demand has shaped the evolution of cellular design.…”

Mutation of Murine Adenylate Kinase 7 Underlies a Primary Ciliary Dyskinesia Phenotype

“…ATP hydrolysis is required not only to confer motility through the action of dynein ATPases, but also for transport of axonemal components necessary for elongation and maintenance of cilia and flagella (18,19). A number of enzymatic relay mechanisms using ATP regeneration have been proposed to transport the high-energy phosphate from mitochondria along the length of the axoneme (20,21). Members of the adenylate kinase (AK) family (EC2.7.4.3) have been postulated to provide an efficient way to relay energy to cellular compartments distal to sites of ATP production (22), and studies on flagellated protozoa (23,24) have suggested an essential role of AK isoforms in ciliary function and homeostasis.…”

Anti-Fertilization Activity of a Spirocyclic Sesquiterpene Isocyanide Isolated from the Marine SpongeGeodia exiguaand Related Compounds

“…2A, quiescent dry sperm accumulated phosphocreatine (PCr), but had low levels of P i . 25,27) When the sperm were diluted to 25% in seawater, a decrease in PCr and an increase in P i were observed (Fig. 2B), accompanied by sperm mobilization.…”

“…This coupling depends on the transport of high-energy phosphate compounds from the mitochondria to a flagellar axoneme, mediated by the phosphocreatine energy shuttle. 25,26) To analyze phosphate metabolites of the 1-immobilized starfish sperm, we assigned 31 P signals due to inorganic phosphate (P i ) and high-energy phosphate compounds in intact starfish sperm in the 31 P NMR spectra. As shown in Fig.…”