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Annexin I modulates cell functions by controlling intracellular calcium release
B M Frey1, B F Reber, B S Vishwanath
1Division of Nephrology and Hypertension and. Institute of Pharmacology, University of Berne, CH-3010 Switzerland. brigette.frey@dkf2.unibe.ch
Summary
Annexin I protein controls intracellular calcium release, impacting cell functions and tumor growth. Overexpression blocks calcium release, altering cell adhesion and promoting tumor growth, while down-regulation has the opposite effect.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Annexin I is an intracellular protein with known calcium and phospholipid-binding properties.
- Its precise in vivo function remains largely unelucidated.
Purpose of the Study:
- To investigate the in vivo role of Annexin I in modulating cellular functions.
- To determine the effect of Annexin I expression levels on intracellular calcium signaling and tumor development.
Main Methods:
- Stable transfection of MCF-7 cells with Annexin I in sense and antisense orientations.
- Assessment of intracellular calcium release upon receptor stimulation (purinergic, bradykinin).
- Evaluation of phospholipase C, phospholipase A2, and E-cadherin activities, cell adhesion, and tumor growth in vivo (nude mice, soft agar assay).
Main Results:
- Overexpression of Annexin I abrogated calcium release in response to receptor stimulation.
- Down-regulation of Annexin I led to rapid calcium release.
- Impaired calcium release correlated with reduced phospholipase C and A2 activities, decreased E-cadherin, altered cell adhesion, and enhanced tumor growth.
- Antisense transfection resulted in smaller tumors with more differentiated cells compared to sense transfection.
Conclusions:
- Annexin I plays a critical role in regulating intracellular calcium release.
- Modulation of Annexin I levels significantly impacts cellular functions, including adhesion and proliferation.
- Annexin I acts as a key regulator of cell behavior and tumor progression through control of calcium signaling.