Eric E. Lloyd, Ph.D.
Postdoctoral Research Associate
- B.S.: University of California, Davis, Physiology, 1996
- Ph.D.: Baylor College of Medicine, Cardiovascular Physiology, 2005
Cellular and molecular mechanisms involved in the regulation of arterial blood flow. Molecular cloning and expression of potassium channels expressed in vascular smooth muscle. Cardiovascular phenotyping of mice lacking Two-Pore Domain potassium channels (K2P).
Description of Research
We have recently demonstrated that TWIK-2, a two-pore domain potassium channel, is highly expressed in rat middle cerebral artery (MCA) (AJP 291:H770, 2006). In this study, we cloned TWIK-2 from rat MCA and expressed it heterologously as a fusion protein to GFP for characterization. Direct fluorescence analysis by deconvolution microscopy in stably transfected CHO cells revealed that GFP-rTWIK-2 localized to the plasma membrane in a punctate pattern by 72 hours after passaging. Stable transfectants of GFP-rTWIK-2 were analyzed by whole-cell electrophysiology. Whole cell currents were 30-fold greater than the nontransfected control group, were non-rectifying in physiological K+, but were inwardly rectifying in symmetrical K+. The observed reversal potentials in different concentrations of extracellular K+ were similar to the theoretical reversal potentials. In physiological K+, membrane potential was -81 ± 0.5 mV (n=13) for transfected and -51 ± 2.5 mV (n=16) for control cells. 1 mM BaCl2 inhibited currents by 90 ± 1% with a calculated IC50 of 86 mM (n=5). The TWIK-2 currents were minimally affected by 10 mM TEA, 3 mM 4-AP, and 10 mM glibenclamide (n=3). Arachidonic acid (100 mM) increased the currents 88 ± 15% (n=6). PKA inhibition with 100 nM H-89, a competitive PKA inhibitor, decreased baseline currents by 49 ± 11% (n=3). For PKC, activation with 400 nM PMA resulted in a 44 ± 20% (n=3) decrease in whole cell currents. Since vascular smooth muscle of the rat MCA expresses a functional TWIK-2 channel, TWIK-2 has the potential of being an important regulator of vascular tone.
- Namiranian K, Lloyd EE, Crossland RF, Marrelli SP, Taffet GE, Reddy AK, Hartley CJ, Bryan RM Jr. Cerebrovascular responses in mice deficient in the potassium channel, TREK-1. Am J Physiol Regul Integr Comp Physiol. 2010 Mar 31.
- Reddy AK, Namiranian K, Lloyd EE, Bryan RM, Taffet GE, Hartley CJ. Effect of isoflurane on aortic impedance in mice. Conf Proc IEEE Eng Med Biol Soc. 2009;2009:1104-5.
- Lloyd EE, Marrelli SP, Namiranian K, Bryan RM Jr. Characterization of TWIK-2, a two-pore domain K+ channel, cloned from the rat middle cerebral artery. Exp Biol Med. 2009 Dec;234(12):1493-502.
Lloyd EE, Marrelli SP, Bryan RM Jr. cGMP does not activate two-pore domain K+ channels in cerebro- vascular smooth muscle. Am J Physiol Heart Circ Physiol.. 2009 Jun;296(6):H1774-80.
- Gaubatz JW, Gillard BK, Massey JB, Hoogeveen RC, Huang M, Lloyd EE, Pownall HJ. Dynamics of dense electronegative low density lipoproteins and their preferential association of lipoprotein phospholipase A2. J Lipid Res. 48(2): p. 348-57, 2007.
- Lloyd EE, Gaubatz JW, Burns AR, Pownall HJ. Sustained Elevations in NEFA Induce COX-2 Activity and Potentiate Macrophage Foam Cell Formation. Atherosclerosis. May; 192(1): p. 49-55 2007
- Bryan RM, You J, Phillips SC, Andresen JJ, Lloyd EE, Rogers PA, Dryer SE, Marrelli SP. Evidence for Two-Pore Domain Potassium Channels in Rat Cerebral Arteries. Am J. Physiology: Heart Circ. Physiol. H770-H780, 2006.
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