Annexins as intracellular calcium sensors

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Katia Monastyrskaya1, Eduard B Babiychuk, Andrea Hostettler

  • 1Department of Cell Biology, Institute of Anatomy, University of Bern, 3000 Bern 9, Switzerland. monastyk@ana.unibe.ch <monastyk@ana.unibe.ch>

Cell Calcium
|August 18, 2006
PubMed

Insights

Annexins are calcium-binding proteins that interact with cell membranes. This study reveals their coordinated membrane interactions and calcium sensitivity, suggesting a sophisticated cellular calcium sensing system.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Annexins are a multigene family of calcium (Ca2+) and phospholipid-binding proteins.
  • Their diverse functions are not fully understood, with no consensus on the family's overall role.
  • Understanding annexin behavior in response to calcium is crucial for elucidating their cellular functions.

Purpose of the Study:

  • To map the Ca2+-induced translocations of annexin family members in live cells.
  • To investigate the role of the N-terminus in annexin membrane binding and Ca2+ sensitivity.
  • To explore the potential of annexins as a coordinated Ca2+ sensing system within cells.

Main Methods:

  • Live-cell imaging to track Ca2+-induced protein translocations.
  • Expression of full-length and truncated annexin proteins.
  • Co-expression of annexin 2 with S100A10 to assess its effect on Ca2+ sensitivity.

Main Results:

  • Annexins interact with plasma and internal membrane systems in a coordinated manner.
  • Annexin 2 exhibited the highest Ca2+ sensitivity, followed by annexins 6, 4, and 1.
  • Annexin 2's Ca2+ sensitivity increased upon co-expression with S100A10.
  • Annexins 2 and 6 translocated to the plasma membrane, while annexins 4 and 1 associated with intracellular membranes and the nuclear envelope upon Ca2+ elevation.
  • N-terminal truncation modulated Ca2+ sensitivity differently for annexin 1 and annexin 2.

Conclusions:

  • Annexins form a sophisticated Ca2+ sensing system within cells.
  • Their coordinated membrane interactions suggest a regulatory role in cellular signaling pathways.
  • The differential Ca2+ sensitivity and localization of annexins highlight their specialized roles.

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