Caldesmon: A common actin-linked regulatory protein in the smooth muscle and nonmuscle contractile system

1988 ◽  
Vol 37 (3) ◽  
pp. 317-325 ◽  
Author(s):  
Kenji Sobue ◽  
Keiko Kanda ◽  
Toshihiko Tanaka ◽  
Noboru Ueki
Keyword(s):  
Smooth Muscle ◽  
Regulatory Protein ◽  
Contractile System

ATP-sensitive K+ channels in pancreatic, cardiac, and vascular smooth muscle cells

1998 ◽  
Vol 274 (1) ◽  
pp. C25-C37 ◽  
Author(s):  
Hisashi Yokoshiki ◽  
Masanori Sunagawa ◽  
Takashi Seki ◽  
Nicholas Sperelakis
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Myocardial Protection ◽  
Regulatory Protein ◽  
Intrinsic Property ◽  
Sulfonylurea Receptor ◽  
Type K ◽  
Channel Opening ◽  
Electrophysiological Studies ◽  
Atp Sensing

ATP-sensitive K+(KATP) channels are therapeutic targets for several diseases, including angina, hypertension, and diabetes. This is because stimulation of KATP channels is thought to produce vasorelaxation and myocardial protection against ischemia, whereas inhibition facilitates insulin secretion. It is well known that native KATP channels are inhibited by ATP and sulfonylurea (SU) compounds and stimulated by nucleotide diphosphates and K+channel-opening drugs (KCOs). Although these characteristics can be shared with KATP channels in different tissues, differences in properties among pancreatic, cardiac, and vascular smooth muscle (VSM) cells do exist in terms of the actions produced by such regulators. Recent molecular biology and electrophysiological studies have provided useful information toward the better understanding of KATPchannels. For example, native KATPchannels appear to be a complex of a regulatory protein containing the SU-binding site [sulfonylurea receptor (SUR)] and an inward-rectifying K+ channel (Kir) serving as a pore-forming subunit. Three isoforms of SUR (SUR1, SUR2A, and SUR2B) have been cloned and found to have two nucleotide-binding folds (NBFs). It seems that these NBFs play an essential role in conferring the MgADP and KCO sensitivity to the channel, whereas the Kir channel subunit itself possesses the ATP-sensing mechanism as an intrinsic property. The molecular structure of KATPchannels is thought to be a heteromultimeric (tetrameric) assembly of these complexes: Kir6.2 with SUR1 (SUR1/Kir6.2, pancreatic type), Kir6.2 with SUR2A (SUR2A/Kir6.2, cardiac type), and Kir6.1 with SUR2B (SUR2B/Kir6.1, VSM type) [i.e., (SUR/Kir6. x)4]. It remains to be determined what are the molecular connections between the SUR and Kir subunits that enable this unique complex to work as a functional KATP channel.

Regulatory Protein of Vascular Smooth Muscle

1976 ◽  
Vol 80 (4) ◽  
pp. 899-901 ◽  
Author(s):  
Nobuo ITO ◽  
Takuji TAKAGI ◽  
Ken HOTTA
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Regulatory Protein

Agonist-induced association of tropomyosin with protein kinase Cα in colonic smooth muscle

2005 ◽  
Vol 288 (2) ◽  
pp. G268-G276 ◽  
Author(s):  
Sita Somara ◽  
Haiyan Pang ◽  
Khalil N. Bitar
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Thin Filament ◽  
Regulatory Protein ◽  
Direct Interaction ◽  
Muscle Cells ◽  
Smooth Muscle Contraction ◽  
Particulate Fraction ◽  
Calcium Dependent

Smooth muscle contraction regulated by myosin light chain phosphorylation is also regulated at the thin-filament level. Tropomyosin, a thin-filament regulatory protein, regulates contraction by modulating actin-myosin interactions. Present investigation shows that acetylcholine induces PKC-mediated and calcium-dependent phosphorylation of tropomyosin in colonic smooth muscle cells. Our data also shows that acetylcholine induces a significant and sustained increase in PKC-mediated association of tropomyosin with PKCα in the particulate fraction of colonic smooth muscle cells. Immunoblotting studies revealed that in colonic smooth muscle cells, there is no significant change in the amount of tropomyosin or actin in particulate fraction in response to acetylcholine, indicating that the increased association of tropomyosin with PKCα in the particulate fraction may be due to acetylcholine-induced translocation of PKCα to the particulate fraction. To investigate whether the association of PKCα with tropomyosin was due to a direct interaction, we performed in vitro direct binding assay. Tropomyosin cDNA amplified from colonic smooth muscle mRNA was expressed as GST-tropomyosin fusion protein. In vitro binding experiments using GST-tropomyosin and recombinant PKCα indicated direct interaction of tropomyosin with PKCα. PKC-mediated phosphorylation of tropomyosin and direct interaction of PKCα with tropomyosin suggest that tropomyosin could be a substrate for PKC. Phosphorylation of tropomyosin may aid in holding the slided tropomyosin away from myosin binding sites on actin, resulting in actomyosin interaction and sustained contraction.

Effects of calponin on isometric force and shortening velocity in permeabilized taenia coli smooth muscle

1996 ◽  
Vol 270 (2) ◽  
pp. C481-C487 ◽  
Author(s):  
K. Obara ◽  
P. T. Szymanski ◽  
T. Tao ◽  
R. J. Paul
Keyword(s):  
Smooth Muscle ◽  
Light Chain ◽  
Isometric Force ◽  
Dependent Manner ◽  
Taenia Coli ◽  
Shortening Velocity ◽  
Muscle Contractility ◽  
Smooth Muscle Contractility ◽  
Contractile System ◽  
Cross Bridges

Calponin, a thin filament-associated protein, inhibits actomyosin adenosinetriphosphatase in solution and has been suggested to modulate smooth muscle contractility. We used permeabilized guinea pig taenia coli smooth muscle to investigate whether calponin can modulate actin-myosin interaction in a more organized contractile system. Fibers were permeabilized with Triton X-100 and glycerol, which permit access of large macromolecules to the contractile apparatus. For contractures elicited by Ca2+ (6.6 microM + 0.1 microM calmodulin), the recombinant alpha-isoform of chicken gizzard calponin (CaP) decreased isometric force (Fo) and unloaded shortening velocity (Vus) in a dose-dependent manner; 1 microM CaP had minimal effects on force (< 10%) but reduced Vus by approximately 50% and 10 microM CaP reduced Fo to 27% of control and Vus to near zero levels. To eliminate any effects of the binding of calmodulin by CaP and consequent inhibition of myosin light chain kinase activity, we also studied fibers activated by thiophosphorylation of the myosin regulatory light chain. Fo was only moderately inhibited, remaining at approximately 75% of control in the presence of CaP (10 microM), whereas Vus was reduced to 32% of control. A similar inhibition was obtained with a mutant (CaPcys175) that retains the ability to bind to actin. CaP phosphorylated by protein kinase C and CaPcys175 mutant labeled with 1,5-IAEDANS, which bind actin poorly, were not effective inhibitors. Our results indicate that 1) CaP more strongly inhibits Vus (approximately cross-bridge cycle rate) than Fo (approximately number of activated cross bridges) and 2) the effects of CaP are related to its binding to actin. Thus the function of CaP in regulation of smooth muscle contractility may be more strongly related to its function as a modulator of velocity, as related to the "latch state," than as an "on-off" switch.

Effects of halothane on the relationship between cytosolic calcium and force in airway smooth muscle

1994 ◽  
Vol 266 (2) ◽  
pp. L199-L204 ◽  
Author(s):  
K. A. Jones ◽  
G. Y. Wong ◽  
R. R. Lorenz ◽  
D. O. Warner ◽  
G. C. Sieck
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Isometric Force ◽  
Cytosolic Calcium ◽  
Simultaneous Recording ◽  
Physiological Salt Solution ◽  
Response Curves ◽  
Fura 2 ◽  
Contractile System ◽  
Superfusion System

The mechanism of the direct relaxing effect of halothane on airway smooth muscle may involve a decrease in 1) cytosolic calcium concentration ([Ca2+]i) and/or 2) the force produced for a given [Ca2+]i (i.e., the “sensitivity” of the myofibrillar contractile system to Ca2+). This study was conducted to test the hypothesis that halothane reduces the sensitivity of the myofibrillar contractile system to Ca2+ during muscarinic receptor stimulation of canine tracheal smooth muscle. Isolated smooth muscle strips were mounted in a photometric superfusion system, stretched to their optimal length for force development, and loaded with the fluorescent Ca2+ indicator, fura 2, for simultaneous recording of fura 2 fluorescence and isometric force. Emission fluorescence intensities due to excitation at 340 (F340)- and 380 (F380)-nm wavelengths were measured and F340/F380 was used as an index of [Ca2+]i. After superfusion with Ca(2+)-free physiological salt solution (PSS) containing 1 or 100 microM acetylcholine (ACh), two consecutive cumulative concentration-response curves to CaCl2 (0.01–2.4 mM) were generated for each strip; one curve was generated in the presence of halothane. In strips stimulated with 1 (n = 6) or 100 (n = 6) microM ACh, the cumulative addition of CaCl2 to the Ca(2+)-free PSS caused concentration-dependent increases in both F340/F380 and force. In strips stimulated with 1 microM ACh, 2.4 +/- 0.3% halothane proportionally attenuated increases in both F340/F380 and force.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanisms of contractile system sensitization of circular smooth muscle of canine colon

1992 ◽  
Vol 103 (4) ◽  
pp. 1381
Author(s):  
W.T. Gerthoffer ◽  
M. Hamelin ◽  
I.L.O. Buxton ◽  
L. Zhang
Keyword(s):  
Smooth Muscle ◽  
Circular Smooth Muscle ◽  
Contractile System
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