Making a New Tail

Science's STKE  27 Mar 2007:
Vol. 2007, Issue 379, pp. tw100
DOI: 10.1126/stke.3792007tw100

Adams et al. identified the V-ATPase H+ pump in a pharmacological screen for ion transporters involved in Xenopus larval tail regeneration. When the pumping activity of the V-ATPase was inhibited with concanamycin, tail regeneration was inhibited, whereas primary tail development and wound healing were unaffected. Using a dominant-negative V-ATPase, the same inhibition of regeneration was observed, confirming V-ATPase as the target. Expression of a yeast P-type H+ pump, which is insensitive to concanamycin, was localized to the plasma membrane and also prevented concanamycin inhibition of regeneration, confirming that it was transport of H+ efflux at the plasma membrane that was important for regeneration. Six hours after amputation, the abundance of the mRNA for the c subunit of the V-ATPase had increased, and by 24 hours after amputation the H+ pump was abundant in the plasma membrane of the cells of the regeneration bud. The cells of the regeneration bud were depolarized six hours after amputation; however, by 24 hours after amputation, the cells were repolarized, which is consistent with the hyperpolarizing activity of the H+ pump. Furthermore, depolarization of the tails using a drug that converts the Na+,K+ ATPase into a Na+/K+ channel also inhibited regeneration, supporting the concept that membrane voltage is a critical regulator of regeneration. Inhibition of the H+ pump decreased the number of proliferating cells in the regeneration bud and inhibited the expression of the KCNK1 gene, which encodes a K+ channel that is expressed at early stages of regeneration (12 hours after amputation). Axon patterning in the regeneration bud was also aberrant when the H+ pump activity was inhibited. Thus, H+ pump activity contributes to changes in membrane potential that are important for regulation of gene expression, cell proliferation, and proper patterning of the new tissues.

D. S. Adams. A. Masi, M. Levin, H+ pump-dependent changes in membrane voltage are an early mechanism necessary and sufficient to induce Xenopus tail regeneration. Development 134, 1323-1335 (2007). [Abstract] [Full Text]