Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.48 (transcriptase)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Magnesium modulates vascular smooth muscle cell (VSMC) function. However, molecular mechanisms regulating VSMC Mg2+ remain unknown. Using biochemical, pharmacological, and genetic tools, the role of transient receptor potential membrane melastatin 7 (TRPM7) cation channel in VSMC Mg2+ homeostasis was evaluated. Rat, mouse, and human VSMCs were studied. Reverse transcriptase polymerase chain reaction and immunoblotting demonstrated TRPM7 presence in VSMCs (membrane and cytosol). Angiotensin II (Ang II) and aldosterone increased TRPM7 expression. Gene silencing using small interfering RNA (siRNA) against TRPM7, downregulated TRPM7 (mRNA and protein). Basal [Mg2+]i, measured by mag fura-2AM, was reduced in siRNA-transfected cells (0.39+/-0.01 mmol/L) versus controls (0.54+/-0.01 mmol/L; P<0.01). Extracellular Mg2+ dose-dependently increased [Mg2+]i in control cells (Emax 0.70+/-0.02 mmol/L) and nonsilencing siRNA-transfected cells (Emax 0.71+/-0.04 mmol/L), but not in siRNA-transfected cells (Emax 0.5+/-0.01 mmol/L). The functional significance of TRPM7 was evaluated by assessing [Mg2+]i and growth responses to Ang II in TRPM7 knockdown cells. Acute Ang II stimulation decreased [Mg2+]i in control and TRPM7-deficient cells in a Na+-dependent manner. Chronic stimulation increased [Mg2+]i in control, but not in siRNA-transfected VSMCs. Ang II-induced DNA and protein synthesis, measured by 3[H]-thymidine and 3[H]-leucine incorporation, respectively, were increased in control and nonsilencing cells, but not in TRPM7 knockdown VSMCs. Our data indicate that VSMCs possess membrane-associated, Ang II-, and aldosterone-regulated TRPM7 channels, which play a role in regulating basal [Mg2+]i, transmembrane Mg2+ transport and DNA and protein synthesis. These novel findings identify TRPM7 as a functionally important regulator of Mg2+ homeostasis and growth in VSMCs.
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PMID:Transient receptor potential melastatin 7 ion channels regulate magnesium homeostasis in vascular smooth muscle cells: role of angiotensin II. 1559 Dec 30

The calcium-sensing receptor (CaR) is expressed in epithelial ducts of both normal human breast and breast cancer tissue, as well as in the MCF-7 cell line as assessed by immunohistochemistry and Western blot analysis. However, to date, there are no data regarding the transduction pathways of CaR in breast cancer cells. In this study, we show that a CaR agonist, spermine, and increased extracellular Ca(2+) ([Ca(2+)](o)) sequentially activate two inward currents at -80 mV. The first was highly permeable to Ca(2+) and inhibited by 2-aminophenyl borate (2-APB). In contrast, the second was more sensitive to Na(+) and Li(+) than to Ca(2+) and insensitive to 2-APB. Furthermore, intracellular dialysis with high Mg(2+), flufenamic acid or amiloride perfusion was without any effect on the second current. Both currents were inhibited by La(3+). Calcium imaging recordings showed that both [Ca(2+)](o) and spermine induced an increase in intracellular calcium ([Ca(2+)](i)) and that removal of extracellular Ca(2+) or perfusion of 2-APB caused a decline in [Ca(2+)](i). It is well known that stimulation of CaR by an increase in [Ca(2+)](o) or with spermine is associated with activation of phospholipase C (PLC). Inhibition of PLC reduced the [Ca(2+)](o)-stimulated [Ca(2+)](i) increase. Lastly, reverse-transcriptase polymerase chain reaction showed that MCF-7 cells expressed canonical transient receptor potential (TRPCs) channels. Our results suggest that, in MCF-7 cells, CaR is functionally coupled to Ca(2+)-permeable cationic TRPCs, for which TRPC1 and TRPC6 are the most likely candidates for the highly selective Ca(2+) current. Moreover, the pharmacology of the second Na(+) current excludes the involvement of the more selective Na(+) transient receptor potential melastatin (TRPM4 and TRPM5) and the classical epithelial Na(+ )channels.
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PMID:Calcium-sensing receptor stimulation induces nonselective cation channel activation in breast cancer cells. 1704 82

The transient receptor potential-melastatin 8 (TRPM8) is a non-selective Ca2+-permeable channel, activated by cold, membrane depolarization, and different cooling compounds. TRPM8 expression has been found in gut mucosal, submucosal, and muscular nerve endings. Although TRPM8 plays a role in pathological conditions, being involved in visceral pain and inflammation, the physiological functions in the digestive system remain unclear as yet. The aims of the present study were: (i) to verify the TRPM8 expression in human distal colon; (ii) to examine the effects of TRPM8 activation on colonic contractility; (iii) to characterize the mechanism of action. Reverse transcriptase-polymerase chain reaction (RT-PCR) and western blotting were used to analyze TRPM8 expression. The responses of human colon circular strips to different TRPM8 agonists [1-[Dialkyl-phosphinoyl]-alkane (DAPA) 2-5, 1-[Diisopropyl-phosphinoyl]-alkane (DIPA) 1-7, DIPA 1-8, DIPA 1-9, DIPA 1-10, and DIPA 1-12) were recorded using a vertical organ bath. The biomolecular analysis revealed gene and protein expression of TRPM8 in both mucosal and smooth muscle layers. All the agonists tested, except-DIPA 1-12, produced a concentration-dependent decrease in spontaneous contraction amplitude. The effect was significantly antagonized by 5-benzyloxytryptamine, a TRPM8 antagonist. The DIPA 1-8 agonist resulted in the most efficacious and potent activation among the tested molecules. The DIPA 1-8 effects were not affected by tetrodotoxin, a neural blocker, but they were significantly reduced by tetraethylammonium chloride, a non-selective blocker of K+ channels. Moreover, iberiotoxin, a blocker of the large-conductance Ca2+-dependent K+-channels, but not apamin, a blocker of small-conductance Ca2+-dependent K+ channels, significantly reduced the inhibitory DIPA 1-8 actions. The results of the present study demonstrated that TRPM8 receptors are also expressed in human distal colon in healthy conditions and that ligand-dependent TRPM8 activation is able to reduce the colonic spontaneous motility, probably by the opening of the large-conductance Ca2+-dependent K+-channels.
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PMID:TRPM8 Channel Activation Reduces the Spontaneous Contractions in Human Distal Colon. 3275 47