Intercellular communication inAzolla roots: II. Electrical coupling

PROTOPLASMA ◽  
1982 ◽  
Vol 111 (2) ◽  
pp. 151-160 ◽  
Author(s):  
R. L. Overall ◽  
B. E. S. Gunning
Keyword(s):  
Intercellular Communication ◽  
Electrical Coupling

scholarly journals Proteoglycans and glycosaminoglycans induce gap junction synthesis and function in primary liver cultures.

1987 ◽  
Vol 105 (1) ◽  
pp. 541-551 ◽  
Author(s):  
D C Spray ◽  
M Fujita ◽  
J C Saez ◽  
H Choi ◽  
T Watanabe ◽  
...  
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Intercellular Communication ◽  
Electrical Coupling ◽  
Sulfated Polysaccharides ◽  
Sulfate Proteoglycan ◽  
Dye Coupling ◽  
Junction Protein ◽  
Gap Junction Protein ◽  
In Cells

Intercellular communication via gap junctions, as measured by dye and electrical coupling, disappears within 12 h in primary rat hepatocytes cultured in serum-supplemented media or within 24 h in cells in a serum-free, hormonally defined medium (HDM) designed for hepatocytes. Glucagon and linoleic acid/BSA were the primary factors in the HDM responsible for the extended life span of the electrical coupling. After 24 h of culture, no hormone or growth factor tested could restore the expression of gap junctions. After 4-5 d of culture, the incidence of coupling was undetectable in a serum-supplemented medium and was only 4-5% in HDM alone. However, treatment with glycosaminoglycans or proteoglycans of 24-h cultures, having no detectable gap junction protein, resulted in synthesis of gap junction protein and of reexpression of electrical and dye coupling within 48 h. Most glycosaminoglycans were inactive (heparan sulfates, chondroitin-6 sulfates) or only weakly active (dermatan sulfates, chondroitin 4-sulfates, hyaluronates), the weakly active group increasing the incidence of coupling to 10-30% with the addition of 50-100 micrograms/ml of the factor. Treatment of the cells with 50-100 micrograms/ml of heparins derived from lung or intestine resulted in cells with intermediate levels of coupling (30-50%). By contrast, 10-20 micrograms/ml of chondroitin sulfate proteoglycan, dermatan sulfate proteoglycan, or liver-derived heparin resulted in dye coupling in 80-100% of the cells, with numerous cells showing dye spread from a single injected cell. Sulfated polysaccharides of glucose (dextran sulfates) or of galactose (carrageenans) were inactive or only weakly active except for lambda-carrageenan, which induced up to 70% coupling (albeit no multiple coupling in the cultures). The abundance of mRNA (Northern blots) encoding gap junction protein and the amounts of the 27-kD gap junction polypeptide (Western blots) correlated with the degree of electrical and dye coupling indicating that the active glycosaminoglycans and proteoglycans are inducing synthesis and expression of gap junctions. Thus, proteoglycans and glycosaminoglycans, especially those found in abundance in the extracellular matrix of liver cells, are important in the regulation of expression of gap junctions and, thereby, in the regulation of intercellular communication in the liver. The relative potencies of heparins from different tissue sources at inducing gap junction expression are suggestive of functional tissue specificity for these glycosaminoglycans.

Na-K-ATPase regulates intercellular communication in the vascular wall via cSrc kinase-dependent connexin43 phosphorylation

2017 ◽  
Vol 312 (4) ◽  
pp. C385-C397 ◽  
Author(s):  
Lise Hangaard ◽  
Elena V. Bouzinova ◽  
Christian Staehr ◽  
Vibeke S. Dam ◽  
Sukhan Kim ◽  
...  
Keyword(s):  
Gap Junctions ◽  
Tyrosine Phosphorylation ◽  
Intercellular Communication ◽  
Arterial Wall ◽  
Electrical Coupling ◽  
Input Resistance ◽  
Vascular Wall ◽  
Oscillatory Activity ◽  
A7r5 Cells

Communication between vascular smooth muscle cells (VSMCs) is dependent on gap junctions and is regulated by the Na-K-ATPase. The Na-K-ATPase is therefore important for synchronized VSMC oscillatory activity, i.e., vasomotion. The signaling between the Na-K-ATPase and gap junctions is unknown. We tested here the hypothesis that this signaling involves cSrc kinase. Intercellular communication was assessed by membrane capacitance measurements of electrically coupled VSMCs. Vasomotion in isometric myograph, input resistance, and synchronized [Ca2+]i transients were used as readout for intercellular coupling in rat mesenteric small arteries in vitro. Phosphorylation of cSrc kinase and connexin43 (Cx43) were semiquantified by Western blotting. Micromole concentration of ouabain reduced the amplitude of norepinephrine-induced vasomotion and desynchronized Ca2+ transients in VSMC in the arterial wall. Ouabain also increased input resistance in the arterial wall. These effects of ouabain were antagonized by inhibition of tyrosine phosphorylation with genistein, PP2, and by an inhibitor of the Na-K-ATPase-dependent cSrc activation, pNaKtide. Moreover, inhibition of cSrc phosphorylation increased vasomotion amplitude and decreased the resistance between cells in the vascular wall. Ouabain inhibited the electrical coupling between A7r5 cells, but pNaKtide restored the electrical coupling. Ouabain increased cSrc autophosphorylation of tyrosine 418 (Y418) required for full catalytic activity whereas pNaKtide antagonized it. This cSrc activation was associated with Cx43 phosphorylation of tyrosine 265 (Y265). Our findings demonstrate that Na-K-ATPase regulates intercellular communication in the vascular wall via cSrc-dependent Cx43 tyrosine phosphorylation.

The α2 isoform of the Na,K-pump is important for intercellular communication, agonist-induced contraction, and EDHF-like response in rat mesenteric arteries

2012 ◽  
Vol 303 (1) ◽  
pp. H36-H46 ◽  
Author(s):  
Vladimir V. Matchkov ◽  
Nina Moeller-Nielsen ◽  
Vibeke Secher Dam ◽  
Zahra Nourian ◽  
Donna M. Briggs Boedtkjer ◽  
...  
Keyword(s):  
Intercellular Communication ◽  
Electrical Coupling ◽  
Vascular Wall ◽  
Mesenteric Arteries ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Small Arteries ◽  
Development In Vitro

The specific role of different isoforms of the Na,K-pump in the vascular wall is still under debate. We have previously suggested that the α2 isoform of the Na,K-pump (α2), Na+, Ca2+-exchange (NCX), and connexin43 form a regulatory microdomain in smooth muscle cells (SMCs), which controls intercellular communication and contractile properties of the vascular wall. We have tested this hypothesis by downregulating α2 in cultured SMCs and in small arteries with siRNA in vivo. Intercellular communication was assessed by using membrane capacitance measurements. Arteries transfected in vivo were tested for isometric and isobaric force development in vitro; [Ca2+]i was measured simultaneously. Cultured rat SMCs were well-coupled electrically, but 10 μM ouabain uncoupled them. Downregulation of α2 reduced electrical coupling between SMCs and made them insensitive to ouabain. Downregulation of α2 in small arteries was accompanied with significant reduction in NCX expression. Acetylcholine-induced relaxation was not different between the groups, but the endothelium-dependent hyperpolarizing factor-like component of the response was significantly diminished in α2-downregulated arteries. Micromolar ouabain reduced in a concentration-dependent manner the amplitude of norepinephrine (NE)-induced vasomotion. Sixty percent of the α2-downregulated arteries did not have vasomotion, and vasomotion in the remaining 40% was ouabain insensitive. Although ouabain increased the sensitivity to NE in the control arteries, it had no effect on α2-downregulated arteries. In the presence of a low NE concentration the α2-downregulated arteries had higher [Ca2+]i and tone. However, the NE EC50 was reduced under isometric conditions, and maximal contraction was reduced under isometric and isobaric conditions. The latter was caused by a reduced Ca2+-sensitivity. The α2-downregulated arteries also had reduced contraction to vasopressin, whereas the contractile response to high K+ was not affected. Our results demonstrate the importance of α2 for intercellular coupling in the vascular wall and its involvement in the regulation of vascular tone.

Osmolarity reduction transiently increases K+ conductance of confluent rat hepatocytes in primary culture

1992 ◽  
Vol 263 (6) ◽  
pp. G913-G919 ◽  
Author(s):  
F. Wehner ◽  
G. Beetz ◽  
S. Rosin-Steiner
Keyword(s):  
Intercellular Communication ◽  
Primary Cultures ◽  
Electrical Coupling ◽  
Rat Hepatocytes ◽  
Membrane Resistance ◽  
Membrane Voltage ◽  
Voltage Response ◽  
High K ◽  
Ion Substitution ◽  
Specific Membrane

Rat hepatocytes in confluent primary cultures were impaled with conventional microelectrodes. Reducing extracellular osmolarity by 80 mosmol/l leads to a transient hyperpolarization of cell membranes (maximum after 5 min) from -40 +/- 4 to -51 +/- 2 mV (n = 7). This hyperpolarization is blocked by 1 mmol/l Ba2+ and 0.5 mmol/l quinine. In ion substitution experiments, increasing K+ 10-fold (from 2.7 to 27 mmol/l) depolarizes membrane voltage by 9 +/- 2 mV in normosmotic solutions. In hyposmotic solutions this depolarization is increased to 20 +/- 1 mV at the time of maximum hyperpolarization and decreases thereafter to 8 +/- 2 mV (n = 4). Cable analysis reveals a transient decrease of specific membrane resistance that exactly parallels the increase in membrane voltage response to high K+. In addition, electrical coupling between cells continuously decreases under hyposmotic conditions, indicating that intercellular communication is affected. Reducing Cl- 100-fold (from 116.5 to 1.2 mmol/l; HCO(3-)-free solutions) depolarizes hepatocytes by 24 +/- 3 mV under normosmotic conditions. In hyposmotic solutions, this effect is increased to 39 +/- 4 mV at maximum hyperpolarization and decreases again to 26 +/- 3 mV (n = 8). This transient increase in the voltage response to Cl- removal is abolished by 0.5 mmol/l quinine (n = 5) and 1 mmol/l Ba2+ (n = 5), suggesting that it is indirect via changes in K+ conductance. This concept is corroborated by ion substitution experiments (HCO(3-)-free conditions), which show that under hyposmotic conditions voltage response to high K+ is considerably decreased in low Cl- solutions.(ABSTRACT TRUNCATED AT 250 WORDS)

Sign in / Sign up

Export Citation Format

Share Document