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3073, cat. 5
CALCIUM CHANNEL EXPRESSION IN VASCULAR SMOOTH MUSCLE
CELLS IS MODULATED BY CALCIUM CHANNEL SUBUNIT GENE
TRANSFER
S. Telemaque, S.E. Flynn, T. Grain, M. Liu, J.D. Marsh
University of Arkansas for Medical Sciences, Little Rock, AR, USA
Vascular smooth muscle (VSM) tone and thus blood pressure is regulated by calcium
(Ca) entry through L-type calcium channels (LTCC) and Ca release from intracellular
stores through IP3 receptors (IP3R). Therefore, gene delivery to VSM to produce
sustained modulation of Ca entry and/or release is an attractive and novel therapeutic
approach to treat hypertension.
Methods: Plasmids encoding the wild type beta subunit (Full) or a truncated subunit,
comprising only the beta-interacting domain (BID, dominant-negative construct)
cDNA fused to GFP, were constructed under the control of a smooth muscle cellspecific promoter (SM22) and were transfected into A7r5 (VSM) and HL-1 (cardiac)
cells. 48 hours following transfection cells were imaged by fluorescence microscopy
and protein expression was determined by immunoblot. We determined specificity of
gene expression using the VSM-specific promoter.
Results: HL-1 cells expressed barely detectable amounts of the delivered genes. In
whole cell lysates of A7r5 cells we observed that alpha1c subunit protein levels were
elevated when Full was transfected compared to GFP (control) whereas levels were
not altered in cells expressing BID. IP3R protein expression was also increased after
the Full beta subunit was delivered in A7r5 cells. Regulation of the alpha1c subunit
and IP3R was selective because the LTCC alpha2-deltaƒnsubunit expression was not
altered by Full or BID gene delivery.
Conclusion: this strategy produces tissue-specific coordinate regulation of alpha1c
subunits and IP3R. Physiological consequences of overexpression of wild-type and
dominant negative beta subunits on channel function are currently under investigation.