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Roles of PMCA Isoforms in Ca2+-Homeostasis and Contractility of Bladder Smooth Muscle: Evidence from PMCA Gene-Ablated Mice

Liu, Li
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1178307168

Abstract Details

2007, PhD, University of Cincinnati, Medicine : Molecular and Cellular Physiology.
Plasma membrane Ca2+ ATPase (PMCA) has four main isoforms encoded by different genes, but only PMCA1 and 4 are expressed in smooth muscle. We investigated the role and relation of the PMCA, sarco-(endo)plasmic reticulum Ca2+ ATPase (SERCA2) and Na+/Ca2+ exchanger (NCX) in urinary bladder smooth muscle (UBSM) contractility and Ca2+ homeostasis, by using Pmca1 heterozygous (Pmca1+/-), Pmca4 heterozygous (Pmca4+/-), Pmca4 null mutant mice (Pmca4-/-) and heterozygous Pmca1 and homozygous Pmca4 double gene-targeted (Pmca1+/-Pmca4-/-) mice. The gene manipulation did not alter the amounts of SERCA2 or NCX. Based on the half-time of relaxation rate after KCl stimulation, the contribution of PMCA to relaxation was calculated to be at least 25%, SERCA2 20% and NCX 70% (Liu et al., 2006). When [Ca2+]i and contractility were simultaneously measured, KCl elicited both larger forces and Ca2+ in Pmca1+/- and Pmca1+/-Pmca4-/-. The responses to carbachol (CCh) were also larger in Pmca1+/-. In contrast, the responses in Pmca4-/- and Pmca1+/-Pmca4-/- to CCh were significantly smaller. Our evidence indicates distinct isoform functions with PMCA1 involved in overall Ca2+-clearance, while PMCA4 is essential for the [Ca2+]i and contractile responses to CCh. We hypothesized that a localized increase of [Ca2+]i in the absence of PMCA4 may inhibit the CCh-receptor-mediated function. CCh-induced contractility after treatments with iberotoxin (IBTX, Ca2+ sensitive K+ channels (BK+Ca) blocker) and 2-aminoethoxydiphenyl borate (2-APB, capacitative Ca2+ entry (CCE) blocker) did not eliminate the difference between WT and Pmca4-/-, indicating that neither BK+Ca channels nor CCE were altered. However, the L-type Ca2+-channel (Cav1.2) blocker nifedipine exhibited significantly less inhibition in Pmca4-/- than in WT and Cav1.2 activators Bay K 8644 and KCl significantly increased the force in Pmca4-/- and restored the force to the same level as in WT. Western blot indicated the expression of Cav1.2 was not changed. Our data indicates the activities of Cav1.2 and ACh-receptor mediated signal transduction may be disrupted by localized increases in [Ca2+]i due to the absence of PMCA4 in Pmca4-/-. Immunocytochemistry of PMCA and Cav1.2 indicates that PMCA1 and PMCA4 isoform have different distribution pattern, with PMCA1 uniformly distributed while PMCA4 punctated, yet, PMCA4 always associated with Cav1.2.
Richard Paul, PhD (Advisor)
Yukisato Ishida, PhD (Other)
Gary Shull, PhD (Other)
Janusz Suszkiw, PhD (Other)
154 p.
PMCA (human gene symbols; ATP2B); SERCA2 (human gene symbols; ATP2A2); NCX; bladder smooth muscle; Ca2+ homeostasis; gene-altered mice. Ca2+ waves; Ca2+ sparks; Fura-PE3; Fluo-4; Indo-1; multi-photon microscopy

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Citations

  • Liu, L. (2007). Roles of PMCA Isoforms in Ca2+-Homeostasis and Contractility of Bladder Smooth Muscle: Evidence from PMCA Gene-Ablated Mice [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1178307168

    APA Style (7th edition)

  • Liu, Li. Roles of PMCA Isoforms in Ca2+-Homeostasis and Contractility of Bladder Smooth Muscle: Evidence from PMCA Gene-Ablated Mice. 2007. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1178307168.

    MLA Style (8th edition)

  • Liu, Li. "Roles of PMCA Isoforms in Ca2+-Homeostasis and Contractility of Bladder Smooth Muscle: Evidence from PMCA Gene-Ablated Mice." Doctoral dissertation, University of Cincinnati, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1178307168

    Chicago Manual of Style (17th edition)

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© 2007, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.