Understanding The Dynamics Of Annexin A6 In Cardiomyocytes
IR@IICB: CSIR-Indian Institute of Chemical Biology, Kolkata
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| Title |
Understanding The Dynamics Of Annexin A6 In Cardiomyocytes
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| Creator |
Banerjee, Priyam
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| Subject |
Cell Biology & Physiology
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| Description |
Deregulations in signaling pathways that control cell-size are prominent in maladaptive cardiomyocyte hypertrophy, a major risk factor in heart failure.Present work explores the intracellular dynamics of annexin A6 (Anxa6), a
protein differentially expressed in cardiomyocyte hypertrophy. Induction of prohypertrophic signaling by acute and chronic exposure of H9c2(2-1) cardiomyocytes to chemical agonists Phenylephrine (PE), Angiotensin II (Ang II) or Isoproterenol (Iso) resulted in profound increment in cell-size and hypertrophy associated phenotypes, as revealed by microscopic and biochemical examinations. Chronic treatments also compromised mitochondrial dynamics
and activated mitochondrial pathways of apoptosis. Anxa6 was upregulated in a phasic fashion in course of acute treatments and in a more linear fashion in
course of chronic treatments. Biophysical and microscopic experiments revealed an oscillatory cytosolic dynamics of the protein in hypertrophied cells that resulted in a differential localization pattern. Anxa6 was progressively distributed from perinuclear compartment to the plasma membrane under acute treatment. Chronic treatments concentrated the protein more to the perinuclear space. In
either scenario, the appearance was granular punctate. Ectopic expression of Anxa6 at controlled levels significantly protected the cardiomyocytes from
hypertrophy-associated increase in cell size and conserved mitochondrial dynamics. However, such expression also rendered the cells vulnerable to apoptosis. Anxa6 knockdown augmented hypertrophic responses and severely
abrogated mitochondrial dynamics in cardiomyocytes. At molecular levels,Anxa6 was found to interact with the anti-hypertrophic candidate ANP, proapoptotic nuclear enzyme Poly-(ADP-ribose) polymerase 1 (Parp1) and the
survival kinase Akt. Capability to interact with such diversely functional candidates enabled Anxa6 to participate in multiple scaffolding events
simultaneously, thereby exhibiting the oscillatory pattern of dynamics. Mutagenesis studies confirmed that Ca2+ was essential for Anxa6 interactions, which occasionally required cholesterol. The Anxa6-ANP interaction was crucial
for ANP mediated counter hypertrophic responses whereas Anxa6-Parp1 and Anxa6-Akt interactions have implications in apoptosis and mitochondrial dynamics. Structurally, interactions of Anxa6 were mediated mostly by its Nterminus
whereas C-terminus was more catalytic, presumably serving to bind Ca2+ required for the interactions. Together, present study depicts a novel mechanistic spectrum of Anxa6 dynamics that helps to regulate equilibrium state
of the homeostatic machineries that dictate life and death decisions in cardiomyocytes.
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| Date |
2014
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| Type |
Thesis
NonPeerReviewed |
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| Format |
application/pdf
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| Identifier |
http://www.eprints.iicb.res.in/2063/1/Priyam_Banerjee_Ph.D._Thesis.pdf
Banerjee, Priyam (2014) Understanding The Dynamics Of Annexin A6 In Cardiomyocytes. PhD thesis, Calcutta University. |
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| Relation |
http://www.eprints.iicb.res.in/2063/
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