ATP enhances repair of hair bundles in sea anemones.
Hair bundle mechanoreceptors of sea anemones are similar to those of the acousticolateralis system of vertebrates (Watson, Mire and Hudson, 1997, Hear. Res. 107, 53-63). Anemone hair bundles are repaired by 'repair proteins' secreted following a complete loss of structural integrity and loss of function caused by 1 h exposure to calcium free seawater. Exogenously supplied repair proteins (RP) restore structural integrity to hair bundles and restore vibration sensitivity in 7-8 min (Watson, Mire and Hudson, 1998, Hear. Res. 115, 119-128). We here report that exogenously supplied ATP enhances the rate by which RP restore vibration sensitivity. A bimodal dose response to ATP indicates maximal enhancement at picomolar and micromolar concentrations of ATP. At these concentrations of ATP, vibration sensitivity is restored in 2 min. These data suggest that at least two ATPases exhibiting different binding affinities for ATP are involved in the repair process. Whereas the higher affinity site is specific for ATP, the lower affinity site does not discriminate between ATP and ADP. Nucleotidase cytochemistry localizes ATPase activity in isolated repair proteins. In the absence of exogenously added RP, sea anemones secrete and consume ATP during the 4 h recovery period after 1 h exposure to calcium free seawater. In the presence of exogenously added RP, ATP is secreted and then consumed within 10 min. Quinacrine cytochemistry localizes possible stores of ATP in the apical cytoplasm of sensory neurons located at the center of the hair bundle. According to our model, ATP is secreted by the sensory neuron after its hair bundle loses structural integrity. Hydrolysis of ATP by repair proteins is essential to the repair process.
Watson
G M
GM
Department of Biology, P.O. Box 42451, University of Southwestern Louisiana, Lafayette, LA 70504-2451, USA. gmw5722@usl.edu
Venable
S
S
Hudson
R R
RR
Repass
J J
JJ
D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D000818:Animals; D005110:Extracellular Space / Q000378:metabolism; D006651:Histocytochemistry; D008465:Mechanoreceptors / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D008854:Microscopy, Electron; D009708:Nucleotidases; D011506:Proteins / Q000502:physiology; D011796:Quinacrine; D012615:Sea Anemones / Q000378:metabolism / Q000502:physiology*; D012623:Seawater; D014732:Vibration
D011506:Proteins; D000255:Adenosine Triphosphate; D009708:Nucleotidases; C030287:nucleotidase; D011796:Quinacrine