Abstract
The β-adrenoceptors (β-ARs) control many cellular processes. Here, we show that β-ARs inhibit calcium depletion-induced cell contractility and subsequent cell detachment of L6 skeletal muscle cells. The mechanism underlying the cell detachment inhibition was studied by using a quantitative cell detachment assay. We demonstrate that cell detachment induced by depletion of extracellular calcium is due to myosin- and ROCK-dependent contractility. The β-AR inhibition of L6 skeletal muscle cell detachment was shown to be mediated by the β2-AR and increased cAMP but was surprisingly not dependent on the classical downstream effectors PKA or Epac, nor was it dependent on PKG, PI3K or PKC. However, inhibition of potassium channels blocks the β2-AR mediated effects. Furthermore, activation of potassium channels fully mimicked the results of β2-AR activation. In conclusion, we present a novel finding that β2-AR signaling inhibits contractility and thus cell detachment in L6 skeletal muscle cells by a cAMP and potassium channel dependent mechanism.
Highlights
Adrenoceptors (ARs) are G protein coupled receptors (GPCRs) expressed in virtually all organs in the body
It is well documented that cAMP can act via the exchange factor directly activated by cAMP (Epac) [1,2], a guanine nucleotide-exchange factor (GEF) that can activate Rap1, a small Ras-like GTPase involved in cellular functions such as cell proliferation, differentiation, apoptosis and adhesion
CHO cells were subjected to calcium-free Phosphate buffered saline (PBS) and after 20 minutes, all cells displayed sperical morphology (Fig. 1A), confirming that CHO-K1 cells can be used in this assay
Summary
Adrenoceptors (ARs) are G protein coupled receptors (GPCRs) expressed in virtually all organs in the body. Stimulation of b2-adrenergic receptors inhibits calcium depletion-induced cell detachment Filamentous actin staining with FITC-conjugated phalloidin was performed in L6 myotubes and results show that PBS treatment leads to cell detachment and isoprenaline treatment prevents this effect (Fig. 2B).
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