Type of Document Dissertation Author Sheela, Thomas Vinaya Author's Email Address tsheela@student.gsu.edu URN etd-08092007-161755 Title REGULATION OF CONNEXIN40 GAP JUNCTIONS Degree Ph.D. Department Biology Advisory Committee
Advisor Name Title Dr. Charles F. Louis Committee Chair Dr. Delon W. Barfuss Committee Member Dr. Jenny J. Yang Committee Member Dr. Vincent Rehder Committee Member Keywords
- Gap junction
- Connexin40
- Intracellular calcium
- Beta-adrenergic regulation.
- Atria
- Chemical ischemia
Date of Defense 2007-06-15 Availability unrestricted Abstract Gap junctions provide direct electrical and biochemical communication betweencardiomyocytes in the heart. Connexin40 (Cx40) is the major connexin in the atria of the
heart and little is known regarding its regulation. Thus, the goal was to investigate the
regulation of Cx40 in both physiological and pathophysiological conditions. The first
objective of this thesis was to determine whether Cx40 gap junctions were regulated by
â-adrenergic receptor activation. Cx40 has previously been shown to be acutely activated
by cAMP, this cAMP-induced increase in Cx40-mediated cell-to-cell dye transfer has
been shown to be effected through the â-adrenergic receptor-adenylyl cyclase- Protein
Kinase A (PKA) pathway in Cx40-transfected HeLa cells. The second objective of this
thesis was to determine whether Cx40 gap junctions were regulated by intracellular Ca2+
concentration ([Ca2+]i ). [Ca2+]i was increased by addition of the ionophore ionomycin
and elevating extracellular calcium [Ca2+]o from 1.8 mM to 21.8 mM. This resulted in an
elevation of [Ca2+]i and effected an inhibition of Cx40-mediated cell-to-cell dye transfer
(IC50 of 500 ± 0.72 nM) which was Calmodulin-dependent. The third objective of this
thesis was to determine whether Cx40 gap junctions were regulated by ischemia.
Inducing ischemia chemically by inhibiting the electron transport chain with sodium
cyanide and glycolysis with iodoacetate and 2-deoxyglucose effected an inhibition of
Cx40-mediated cell-to-cell dye transfer that was shown to be Calmodulin dependent.
The main conclusions of this thesis were: (1) â-adrenergic receptor activation increases
Cx40-mediated cell-to-cell dye transfer which requires the activation of PKA; (2) A
sustained elevation in [Ca2+]i causes a partial inhibition of Cx40 gap junction-mediated
cell-to-cell dye transfer which was Ca2+-and Calmodulin dependent; (3) Chemical
ischemia causes a partial inhibition of Cx40 gap junction-mediated cell-to-cell dye
transfer which was shown to be Calmodulin-dependent.
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