HSP27 phosphorylation and interaction with actin-myosin in smooth muscle contraction

2002 ◽  
Vol 282 (5) ◽  
pp. G894-G903 ◽  
Author(s):  
Khalil N. Bitar
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Signal Transduction Pathway ◽  
Muscle Cells ◽  
Smooth Muscle Contraction ◽  
Thin Filament Regulation ◽  
Kinase C ◽  
Hsp27 Phosphorylation ◽  
Myosin Interaction

We have investigated the role of heat shock protein 27 (HSP27) phosphorylation and the association of HSP27 with contractile proteins actin, myosin, and tropomyosin. Smooth muscle cells were labeled with [32P]orthophosphate. C2-ceramide (0.1 μM), an activator of protein kinase C (PKC), induced a sustained increase in HSP27 phosphorylation that was inhibited by calphostin C. C2-ceramide-induced (0.1 μM) sustained colonic smooth muscle cell contraction was accompanied by significant increases in the association of HSP27 with tropomyosin and in the association of HSP27 with actin. The significant increases occurred at 30 s after stimulation and were sustained at 4 min. Contraction was also associated with strong colocalization of HSP27 with tropomyosin and with actin as observed after immunofluorescent labeling of tropomyosin, actin, and HSP27 followed by confocal microscopy. Transfection of smooth muscle cells with HSP27 phosphorylation mutants indicated that phosphorylation of HSP27 could affect myosin association with actin. In conclusion 1) HSP27 phosphorylation appears to be necessary for reorganization of HSP27 inside the cell and seems to be directly correlated with the PKC signal transduction pathway, and 2) agonist-induced phosphorylation of HSP27 modulates actin-myosin interaction through thin-filament regulation of tropomyosin.

Regulation of smooth muscle contraction in rabbit internal anal sphincter by protein kinase C and Ins(1,4,5)P3

1991 ◽  
Vol 260 (4) ◽  
pp. G537-G542 ◽  
Author(s):  
K. N. Bitar ◽  
C. Hillemeier ◽  
P. Biancani ◽  
K. J. Balazovich
Keyword(s):  
Smooth Muscle ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Smooth Muscle Cells ◽  
Muscle Cells ◽  
Smooth Muscle Contraction ◽  
Threshold Concentration ◽  
Maximal Contraction ◽  
Calmodulin Antagonist ◽  
Kinase C

We have examined the role of protein kinase C (PKC)-beta II and its functional relationship to inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] and intracellular Ca2+ in the contraction of smooth muscle cells from the rabbit internal and sphincter (IAS). PKC-beta (0.1-100 U/ml) and Ins(1,4,5)P3 (10(-9) to 10(-6) M) caused concentration-dependent contraction of IAS smooth muscle cells permeabilized by saponin. The combination of threshold concentrations of Ins(1,4,5)P3 (10(-9) M) and PKC (0.1 U/ml) was more than additive, causing near maximal shortening (28.2 +/- 2.1% decrease in cell length from control). The response to high concentrations of Ins(1,4,5)P3 and PKC used in combination was not greater than the response to either agent alone. The calmodulin antagonist W-7 (10(-9) M) inhibited the maximal contraction induced by Ins(1,4,5)P3 but not contraction caused by PKC, whereas the PKC antagonist H-7 (10(-6) M) inhibited the maximal contraction induced by PKC but not contraction caused by Ins(1,4,5)P3. Threshold doses of the ionophores A23187 (10(-9) M) and ionomycin (0.2 ng/ml) caused little contraction by themselves, but they potentiated the response elicited by a threshold concentration of PKC (0.1 U/ml), inducing maximal contraction. Preincubation of IAS cells with 4 mM Sr2+, which inhibits the release of intracellular Ca2+, abolished the potentiating effect of Ins(1,4,5)P3 and calcium ionophores on PKC, but the calmodulin antagonist W-7 did not. These data suggest that the contractile effect of maximally effective doses of PKC is independent of the effects of Ins(1,4,5)P3. At submaximal concentrations, however, PKC-dependent contraction is potentiated by Ins(1,4,5)P3 or by ionophore-mediated release of intracellular Ca2+ without requiring calmodulin activation.

scholarly journals Phosphorylated HSP27 essential for acetylcholine-induced association of RhoA with PKCα

2004 ◽  
Vol 286 (4) ◽  
pp. G635-G644 ◽  
Author(s):  
Suresh B. Patil ◽  
Mercy D. Pawar ◽  
Khalil N. Bitar
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Muscle Contraction ◽  
Membrane Fraction ◽  
Muscle Cells ◽  
Smooth Muscle Contraction ◽  
Cell Length ◽  
Sustained Contraction ◽  
Hsp 27

Reorganization of the cytoskeleton and association of contractile proteins are important steps in modulating smooth muscle contraction. Heat shock protein (HSP) 27 has significant effects on actin cytoskeletal reorganization during smooth muscle contraction. We investigated the role of phosphorylated HSP27 in modulating acetylcholine-induced sustained contraction of smooth muscle cells from the rabbit colon by transfecting smooth muscle cells with phosphomimic (3D) or nonphosphomimic (3G) HSP27. In 3G cells, the initial peak contractile response at 30 s was inhibited by 25% (24.0 ± 4.5% decrease in cell length, n = 4). The sustained contraction was greatly inhibited by 75% [9.3 ± .9% decreases in cell length ( n = 4)]. Furthermore, in 3D cells, translocation of both PKCα and of RhoA was greatly enhanced and resulted in a greater association of PKCα-RhoA in the membrane fraction. In 3G transfected cells, PKCα and RhoA failed to translocate in response to stimulation with acetylcholine, resulting in an inhibition of association of PKCα-RhoA in the membrane fraction. Studies using GST-RhoA fusion protein indicate that there is a direct association of RhoA with PKCα and with HSP27. The results suggest that phosphorylated HSP27 plays a crucial role in the maintenance of association of PKCα-RhoA in the membrane fraction and in the maintenance of acetylcholine-induced sustained contraction.

scholarly journals Phosphorylated HSP27 modulates the association of phosphorylated caldesmon with tropomyosin in colonic smooth muscle

2006 ◽  
Vol 291 (4) ◽  
pp. G630-G639 ◽  
Author(s):  
Sita Somara ◽  
Khalil N. Bitar
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Thin Filament ◽  
Muscle Cells ◽  
Smooth Muscle Contraction ◽  
Contractile Proteins ◽  
Concomitant Increase ◽  
Thin Filament Regulation ◽  
Hsp 27 ◽  
Actomyosin Interaction

Thin-filament regulation of smooth muscle contraction involves phosphorylation, association, and dissociation of contractile proteins in response to agonist stimulation. Phosphorylation of caldesmon weakens its association with actin leading to actomyosin interaction and contraction. Present data from colonic smooth muscle cells indicate that acetylcholine induced a significant association of caldesmon with PKCα and sustained phosphorylation of caldesmon at ser789. Furthermore, acetylcholine induced significant and sustained increase in the association of phospho-caldesmon with heat-shock protein (HSP)27 with concomitant increase in the dissociation of phospho-caldesmon from tropomyosin. At the thin filament level, HSP27 plays a crucial role in acetylcholine-induced association of contractile proteins. Present data from colonic smooth muscle cells transfected with non-phospho-HSP27 mutant cDNA indicate that the absence of phospho-HSP27 inhibits acetylcholine-induced caldesmon phosphorylation. Our results further indicate that the presence of phospho-HSP27 significantly enhances acetylcholine-induced sustained association of phospho-caldesmon with HSP27 with a concomitant increase in acetylcholine-induced dissociation of phospho-caldesmon from tropomyosin. We thus propose a model whereby upon acetylcholine-induced phosphorylation of caldesmon at ser789, the association of phospho-caldesmon (ser789) with phospho-HSP27 results in an essential conformational change leading to dissociation of phospho-caldesmon from tropomyosin. This leads to the sliding of tropomyosin on actin thus exposing the myosin binding sites on actin for actomyosin interaction.

scholarly journals Actin cytoskeletal dynamics in smooth muscle: a new paradigm for the regulation of smooth muscle contraction

2008 ◽  
Vol 295 (3) ◽  
pp. C576-C587 ◽  
Author(s):  
Susan J. Gunst ◽  
Wenwu Zhang
Keyword(s):  
Extracellular Matrix ◽  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Actin Polymerization ◽  
Muscle Cells ◽  
Smooth Muscle Contraction ◽  
Mechanical Tension ◽  
Muscle Tissues ◽  
Cytoskeletal Dynamics

A growing body of data supports a view of the actin cytoskeleton of smooth muscle cells as a dynamic structure that plays an integral role in regulating the development of mechanical tension and the material properties of smooth muscle tissues. The increase in the proportion of filamentous actin that occurs in response to the stimulation of smooth muscle cells and the essential role of stimulus-induced actin polymerization and cytoskeletal dynamics in the generation of mechanical tension has been convincingly documented in many smooth muscle tissues and cells using a wide variety of experimental approaches. Most of the evidence suggests that the functional role of actin polymerization during contraction is distinct and separately regulated from the actomyosin cross-bridge cycling process. The molecular basis for the regulation of actin polymerization and its physiological roles may vary in diverse types of smooth muscle cells and tissues. However, current evidence supports a model for smooth muscle contraction in which contractile stimulation initiates the assembly of cytoskeletal/extracellular matrix adhesion complex proteins at the membrane, and proteins within this complex orchestrate the polymerization and organization of a submembranous network of actin filaments. This cytoskeletal network may serve to strengthen the membrane for the transmission of force generated by the contractile apparatus to the extracellular matrix, and to enable the adaptation of smooth muscle cells to mechanical stresses. Better understanding of the physiological function of these dynamic cytoskeletal processes in smooth muscle may provide important insights into the physiological regulation of smooth muscle tissues.

Role of atypical protein kinase C isozymes and NF-κB in IL-1β-induced expression of cyclooxygenase-2 in human myometrial smooth muscle cells

2006 ◽  
Vol 210 (3) ◽  
pp. 637-643 ◽  
Author(s):  
Sara V. Duggan ◽  
Tamsin Lindstrom ◽  
Teresa Iglesias ◽  
Phillip R. Bennett ◽  
Giovanni E. Mann ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Smooth Muscle Cells ◽  
Muscle Cells ◽  
Atypical Protein Kinase C ◽  
Induced Expression ◽  
Atypical Protein Kinase ◽  
Kinase C
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