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Updated: Jul 27, 2025

Defining Hsp33's Redox-regulated Chaperone Activity and Mapping Conformational Changes on Hsp33 Using Hydrogen-deuterium Exchange Mass Spectrometry
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Changes in the Activities of H

Keiko Mitsunaga1, Akiko Fujiwara1, Yukio Fujino2

  • 1Department of Biology, School of Education, Waseda University, 1-6-1, Nishiwaseda, Shinjuku-ku, Tokyo 169, Japan.

Development, Growth & Differentiation
|June 7, 2023
PubMed

Insights

Sea urchin micromeres use H+, K+-ATPase to regulate intracellular pH for calcium carbonate spicule formation. This enzyme activity is crucial for biomineralization during early embryonic development.

Area of Science:

  • Developmental Biology
  • Cell Biology
  • Biochemistry

Background:

  • Sea urchin micromeres are key cells for skeletal development.
  • Biomineralization involves precise ion regulation.
  • The role of specific ion pumps in spicule formation is not fully understood.

Purpose of the Study:

  • To investigate the role of H+, K+-ATPase in intracellular pH regulation during sea urchin micromere spiculogenesis.
  • To determine the involvement of H+, K+-ATPase in calcium deposition for spicule formation.

Main Methods:

  • Culture of sea urchin micromeres isolated from 16-cell stage embryos.
  • Assay of H+, K+-ATPase and Na+, K+-ATPase activities over time.
  • Measurement of intracellular pH (pHi) and 45Ca deposition using inhibitors.

Main Results:

  • H+, K+-ATPase activity increased during spicule formation, peaking around 25 hr.
  • Inhibition of H+, K+-ATPase by allylisothiocyanate decreased pHi and blocked 45Ca deposition.
  • Nifedipine blocked 45Ca deposition, and subsequent allylisothiocyanate treatment did not affect pHi.

Conclusions:

  • H+, K+-ATPase plays a critical role in releasing H+ for CaCO3 biomineralization in sea urchin spicule formation.
  • This proton efflux is essential for maintaining intracellular pH homeostasis during CaCO3 production.
  • Na+, K+-ATPase, ouabain, and amiloride appear to have minimal roles in this specific process.

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