Can you blame cold feet on Epac (and Rap1A)? Focus on “Cyclic AMP-Rap1A signaling activates RhoA to induce α2C-adrenoceptor translocation to the cell surface of microvascular smooth muscle cells”

2012 ◽  
Vol 303 (5) ◽  
pp. C488-C489 ◽  
Author(s):  
Martin C. Michel ◽  
Paul A. Insel
Keyword(s):  
Smooth Muscle ◽  
Cyclic Amp ◽  
Cell Surface ◽  
Smooth Muscle Cells ◽  
Muscle Cells

scholarly journals Cyclic AMP-Rap1A signaling mediates cell surface translocation of microvascular smooth muscle α2C-adrenoceptors through the actin-binding protein filamin-2

2013 ◽  
Vol 305 (8) ◽  
pp. C829-C845 ◽  
Author(s):  
Hanaa K. B. Motawea ◽  
Selvi C. Jeyaraj ◽  
Ali H. Eid ◽  
Srabani Mitra ◽  
Nicholas T. Unger ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Plasma Membrane ◽  
Cyclic Amp ◽  
Cell Surface ◽  
Smooth Muscle Cells ◽  
Blood Vessels ◽  
Muscle Cells ◽  
Small Gtpase ◽  
Actin Binding ◽  
Surface Translocation

The second messenger cyclic AMP (cAMP) plays a vital role in vascular physiology, including vasodilation of large blood vessels. We recently demonstrated cAMP activation of Epac-Rap1A and RhoA-Rho-associated kinase (ROCK)-F-actin signaling in arteriolar-derived smooth muscle cells increases expression and cell surface translocation of functional α2C-adrenoceptors (α2C-ARs) that mediate vasoconstriction in small blood vessels (arterioles). The Ras-related small GTPAse Rap1A increased expression of α2C-ARs and also increased translocation of perinuclear α2C-ARs to intracellular F-actin and to the plasma membrane. This study examined the mechanism of translocation to better understand the role of these newly discovered mediators of blood flow control, potentially activated in peripheral vascular disorders. We utilized a yeast two-hybrid screen with human microvascular smooth muscle cells (microVSM) cDNA library and the α2C-AR COOH terminus to identify a novel interaction with the actin cross-linker filamin-2. Yeast α-galactosidase assays, site-directed mutagenesis, and coimmunoprecipitation experiments in heterologous human embryonic kidney (HEK) 293 cells and in human microVSM demonstrated that α2C-ARs, but not α2A-AR subtype, interacted with filamin. In Rap1-stimulated human microVSM, α2C-ARs colocalized with filamin on intracellular filaments and at the plasma membrane. Small interfering RNA-mediated knockdown of filamin-2 inhibited Rap1-induced redistribution of α2C-ARs to the cell surface and inhibited receptor function. The studies suggest that cAMP-Rap1-Rho-ROCK signaling facilitates receptor translocation and function via phosphorylation of filamin-2 Ser2113. Together, these studies extend our previous findings to show that functional rescue of α2C-ARs is mediated through Rap1-filamin signaling. Perturbation of this signaling pathway may lead to alterations in α2C-AR trafficking and physiological function.

scholarly journals Cyclic AMP-Rap1A signaling activates RhoA to induce α2c-adrenoceptor translocation to the cell surface of microvascular smooth muscle cells

2012 ◽  
Vol 303 (5) ◽  
pp. C499-C511 ◽  
Author(s):  
Selvi C. Jeyaraj ◽  
Nicholas T. Unger ◽  
Ali H. Eid ◽  
Srabani Mitra ◽  
N. Paul El-Dahdah ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Cyclic Amp ◽  
Cell Surface ◽  
Smooth Muscle Cells ◽  
Intracellular Signaling ◽  
Muscle Cells ◽  
Small Gtpase ◽  
Hek293 Cells ◽  
Intracellular Camp

Intracellular signaling by the second messenger cyclic AMP (cAMP) activates the Ras-related small GTPase Rap1 through the guanine exchange factor Epac. This activation leads to effector protein interactions, activation, and biological responses in the vasculature, including vasorelaxation. In vascular smooth muscle cells derived from human dermal arterioles (microVSM), Rap1 selectively regulates expression of G protein-coupled α2C-adrenoceptors (α2C-ARs) through JNK-c-jun nuclear signaling. The α2C-ARs are generally retained in the trans-Golgi compartment and mobilize to the cell surface and elicit vasoconstriction in response to cellular stress. The present study used human microVSM to examine the role of Rap1 in receptor localization. Complementary approaches included murine microVSM derived from tail arteries of C57BL6 mice that express functional α2C-ARs and mice deficient in Rap1A (Rap1A-null). In human microVSM, increasing intracellular cAMP by direct activation of adenylyl cyclase by forskolin (10 μM) or selectively activating Epac-Rap signaling by the cAMP analog 8-pCPT-2′- O-Me-cAMP (100 μM) activated RhoA, increased α2C-AR expression, and reorganized the actin cytoskeleton, increasing F-actin. The α2C-ARs mobilized from the perinuclear region to intracellular filamentous structures and to the plasma membrane. Similar results were obtained in murine wild-type microVSM, coupling Rap1-Rho-actin dynamics to receptor relocalization. This signaling was impaired in Rap1A-null murine microVSM and was rescued by delivery of constitutively active (CA) mutant of Rap1A. When tested in heterologous HEK293 cells, Rap1A-CA or Rho-kinase (ROCK-CA) caused translocation of functional α2C-ARs to the cell surface (∼4- to 6-fold increase, respectively). Together, these studies support vascular bed-specific physiological role of Rap1 and suggest a role in vasoconstriction in microVSM.

scholarly journals Agents which increase cyclic AMP have diverse effects on low-density-lipoprotein-receptor function in human vascular smooth-muscle cells and skin fibroblasts

1990 ◽  
Vol 267 (3) ◽  
pp. 607-614 ◽  
Author(s):  
A Middleton ◽  
B Middleton
Keyword(s):  
Smooth Muscle ◽  
Cyclic Amp ◽  
Vascular Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Vascular Smooth Muscle Cells ◽  
Ldl Receptor ◽  
Muscle Cells ◽  
Skin Fibroblasts ◽  
Receptor Expression ◽  
Low Density

Receptor-mediated binding and metabolism of low-density lipoproteins (LDL) in cultured human vascular smooth-muscle cells and skin fibroblasts are altered by increased cellular cyclic AMP concentrations. However, the LDL receptor does not respond to changes in cyclic AMP concentration in a simple manner. The activation of adenylate cyclase with forskolin, or the addition of membrane-permeant cyclic AMP analogues, initially decreases the expression of the LDL receptor, but is followed by a substantial increase in receptor expression after 24 h. This increase does not occur in the presence of inhibitors of RNA or protein synthesis, and is due to doubling of the Bmax. of the LDL receptor, without alteration of its affinity for LDL. By contrast, elevation of cyclic AMP concentration by inhibition of phosphodiesterases results in decreased receptor expression throughout the 24 h period. These two response patterns are reproducible phenomena, consistently observed in low-passaged cells derived from seven unrelated individuals.

scholarly journals Nexuses between the smooth muscle cells of the guinea-pig ileum.

1979 ◽  
Vol 82 (1) ◽  
pp. 239-247 ◽  
Author(s):  
G Gabella ◽  
D Blundell
Keyword(s):  
Smooth Muscle ◽  
Cell Surface ◽  
Guinea Pig ◽  
Smooth Muscle Cells ◽  
Muscle Cell ◽  
Packing Density ◽  
Freeze Fracture ◽  
Muscle Cells ◽  
Guinea Pig Ileum ◽  
Average Cell

The circular musculature of the guinea-pig ileum has been studied by freeze-fracture to analyze quantitatively the gap junctions (nexuses) between its smooth muscle cells. The average cell surface area and cell volume are 5,074 micron 2 and 3,260 micron 3. The packing density of nexuses is 48/1,000 micron 2 of cell surface or approximately 244/muscle cell. Nexuses range in area from less than 0.1 to approximately 1.5 micron 2 and they occupy 0.212% of the cell surface. The average packing density of intramembrane particles or pits in nexuses is approximately 7,200/micron 2 of nexal surface, indicating that there may be approximately 77,000 intercellular channels in the full complement of nexuses of one muscle cell.

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