Contributions of specific TRPS to myometrial calcium entry
Date
2010
Authors
Ulloa, Aida Erendira, author
Sanborn, Barbara M., advisor
Clay, Colin, committee member
Curthoys, Norman P., committee member
Kinnamon, Sue C., committee member
Roess, Deborah A., committee member
Journal Title
Journal ISSN
Volume Title
Abstract
Understanding the mechanisms that regulate contractions in the myometrium during pregnancy may help avoid scenarios such as premature births. During labor, increases in intracellular calcium ([Ca 2+],) have been closely correlated with human myometrium contractions. Extracellular calcium enters the cell through voltage-operated and signal-regulated Ca2+-entry (SRCE) mechanisms and is involved in actions such as stimulating the contractile apparatus and replenishing intracellular Ca^^ stores. In SRCE, activation of some receptors and/or depletion of agonist-sensitive [Ca^^]j-stores stimulates Ca -uptake from the extracellular solution. This and other SRCE mechanisms are all important in providing regulation of calcium homeostasis. Ion channels potentially responsible for SRCE are the canonical transient receptor potential (TRPC) channels. The seven members (TRPC 1-7) are postulated to form hetero- or homotetramers, thus allowing for the formation of a variety of channels possessing different physiological properties. Additional TRPC channel regulation is also provided by STIMl, an endoplasmic reticulum Ca2+ sensor. My studies show that human myometrium expresses higher concentrations of TRPC4 and TRPCl mRNAs relative to other TRPCs as well as expressing STIMl proteins. Furthermore, I have found that specific TRPC proteins are involved in the SRCE pathways when studied in immortalized myometrial PHMl cells. The main objective of this work was to understand the functional role of TRPC 1 and TRPC4 channels in relation to Ca^^ signaling in order to elucidate their relative significance in myometrium. The individual roles for TRPCl and TRPC4 as well as the potential additive effects that a TRPCl plus TRPC4 double knockdown exerted on SRCE were studied in PHMl and primary human uterine smooth muscle (UtSMC) cells. This was achieved through RNAi mechanisms by expression of shRNAs targeting TRPCl, TRPC4, or TRPCl plus TRPC4. The role of STIMl in myometrial Ca2+ dynamics was also investigated by use of STIM1AERM, a dominant negative form of STIM1. The data presented here suggest that both TRPCl and TRPC4 are activated by similar G protein coupled receptor-stimulated Ca^^ entry mechanisms; however, no additive effects were observed by their combined knockdown. Additionally, thapsigargin- and OAGstimulated Ca entry were not affected by either the individual or combined knockdown of TRPCl and TRPC4. In contrast, STIMAERM appeared to induce an inhibitory effect on all three types of SRCE stimulation. These contributions, in addition to the important role in Ca2+ homeostasis played by voltage-operated channels and the influences of Ca^^ pumps, exchangers and potassium channels, provide the myometrium with the ability to respond in specific and precise ways to influences in its environment, both during pregnancy and at the time of parturition.
Description
Covers not scanned.
Print version deaccessioned 2022.
Print version deaccessioned 2022.
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Subject
TRP channels
Myometrium
G proteins -- Receptors