The intermediate filament framework is one of the three cytoskeletal systems in mammalian cells. Its well spread filamentous structure from the nucleus to the plasma membrane is believed to provide protection against various mechanical stresses (1, 2). Intermediate filaments also undergo disassembly/assembly and spatial reorganization in cells in response to external stimulation and during mitosis. The dynamic property of the intermediate filament system plays a fundamental role in mediating changes in cell shape, division, and migration; signaling molecule distribution; and smooth muscle force development (1, 3-7).The dynamic characteristics of the intermediate filament network may be regulated by protein phosphorylation. Vimentin is the most abundant intermediate filament protein in various cell types, including smooth muscle cells (2,5,6). Vimentin phosphorylation in association with vimentin disassembly and spatial reorganization occurs during mitosis or in response to extracellular stimulation (8, 9). In cultured smooth muscle cells, contractile stimulation triggers vimentin phosphorylation at Ser-56 concurrently with vimentin partial disassembly and spatial reorientation (6).The disassembly and spatial reorganization of the vimentin network may regulate the translocation of certain molecules (7, 10, 11). The adapter protein p130 Crk-associated substrate (CAS) 2 has been shown to participate in the signaling processes that regulate smooth muscle contraction and cell migration (12-14). Our recent study has suggested that vimentin phosphorylation and disassembly are related to CAS redistribution during contractile activation of smooth muscle (10). In addition, external stress initiates Rho kinase redistribution associated with vimentin depolymerization in fibroblasts and the translocation of Ca 2ϩ /calmodulin-dependent protein kinase II in differentiated smooth muscle cells, which may be an important event for cell signaling (7, 11).p21-activated kinase (PAK) may be an upstream regulator of the vimentin network (6, 9). In cultured smooth muscle cells, agonist-mediated vimentin phosphorylation at Ser-56 and spatial reorientation of the vimentin network are inhibited by silencing of PAK1, a dominant isoform in smooth muscle (6,15). Additionally, PAK has been implicated in modulating smooth muscle contraction; introduction of an active PAK isoform into smooth muscle potentiates force development at constant intracellular calcium (16). Expression of an inactive PAK1 mutant attenuates migration of cultured smooth muscle cells in response to platelet-derived growth factor (15).In response to external stimulation, PAK undergoes autophosphorylation at Thr-423, which increases PAK activity for substrates (17,18). In addition to the small GTPases Cdc42 and Rac1, the activity of PAK may be regulated by the paxillin kinase linker/PIX (PAK-interacting exchange factor; guanine nucleotide exchange factor) (19 -21). CAS has been shown to interact with the paxillin kinase linker/PIX via CrkII and paxillin (21-* This work was ...

channel inhibition reduced tone at 20 and 80 mmHg, with the greatest effect at high pressure when the vessel is depolarized. In comparison, the effect of T-type Ca 2ϩ channel blockade on myogenic tone was more limited, with their greatest effect at low pressure where vessels are hyperpolarized. Blood flow modeling revealed that the vasomotor responses induced by T-type Ca 2ϩ blockade could alter arterial flow by ϳ20 -50%. Overall, our findings indicate that L-and T-type Ca 2ϩ channels are expressed in cerebral arterial smooth muscle and can be electrically isolated from one another. Both conductances contribute to myogenic tone, although their overall contribution is unequal. influx from the extracellular space (9). Voltage-gated Ca 2ϩ channels are the principal conductances that regulate extracellular Ca 2ϩ influx. These membrane channels are hetero-oligomeric complexes that comprise a pore-forming ␣ 1 -subunit and accessory proteins that influence gating characteristics and protein trafficking (24). The ␣ 1 -subunit is composed of four domains, each of which contain six transmembrane segments, a S4 voltage sensor, and a P loop that confers ion selectivity (21, 50). Molecular studies have identified three classes of ␣ 1 -subunits (Ca v 1-3), and within each category there are several subtypes. Ca v 1/Ca v 2 subunits display electrical properties characteristic of high voltage-activated Ca 2ϩ channels (i.e., L-, P/Q-, N-, and R types) (5). In contrast, Ca v 3 subunits encode for Ca 2ϩ channels activated by lower voltages (i.e., T type) (20,34 channels was more limited and best observed at lower pressures in hyperpolarized vessels. Although the contribution of the channels to tone development is limited, computational

Vascular smooth muscle tone plays a fundamental role in regulating blood pressure, blood flow, microcirculation, and other cardiovascular functions. The cellular and molecular mechanisms by which vascular smooth muscle contractility is regulated are not completely elucidated. Recent studies show that the actin cytoskeleton in smooth muscle is dynamic, which regulates force development. In this review, evidence for actin polymerization in smooth muscle upon external stimulation is summarized. Protein kinases, such as Abl, FAK, Src, and MAP kinase, have been documented to coordinate actin polymerization in smooth muscle. Transmembrane integrins have also been reported to link to signaling pathways modulating actin dynamics. The roles of Rho family of the small GTPases and the actin-regulatory proteins including CAS, N-WASP, the Arp2/3 complex, profilin, and heat shock proteins in regulating actin assembly are discussed. These new findings promote our understanding on how smooth muscle contraction is regulated at cellular and molecular levels.

Abstract-The tyrosine phosphorylated protein Crk-associated substrate (CAS) has previously been shown to participate in the cellular processes regulating dynamic changes in the actin architecture and arterial constriction. In the present study, treatment of rat mesenteric arteries with phenylephrine (PE) led to the increase in CAS tyrosine phosphorylation and the association of CAS with the adapter protein CrkII. CAS phosphorylation was catalyzed by Abl in an in vitro study. To determine the role of Abl tyrosine kinase in arterial vessels, plasmids encoding Abl short hairpin RNA (shRNA) were transduced into mesenteric arteries by chemical loading plus liposomes. Abl silencing diminished increases in CAS phosphorylation on PE stimulation. Previous studies have shown that assembly of the multiprotein compound containing CrkII, neuronal Wiskott-Aldrich Syndrome Protein (N-WASP) and the Arp2/3 (Actin Related Protein) complex triggers actin polymerization in smooth muscle as well as in nonmuscle cells. In this study, Abl silencing attenuated the assembly of the multiprotein compound in resistance arteries on contractile stimulation. Furthermore, the increase in F/G-actin ratios (an index of actin assembly) and constriction on contractile stimulation were reduced in Abl-deficient arterial segments compared with control arteries. However, myosin regulatory light chain phosphorylation (MRLCP) elicited by contractile activation was not inhibited in Abl-deficient arteries. These results suggest that Abl may play a pivotal role in mediating CAS phosphorylation, the assembly of the multiprotein complex, actin assembly, and constriction in resistance arteries. Abl does not participate in the regulation of myosin activation in arterial vessels during contractile stimulation. Key Words: tyrosine kinase Ⅲ actin cytoskeleton Ⅲ contraction Ⅲ vascular smooth muscle Ⅲ adapter protein A ctin cytoskeleton remodeling has recently emerged as an important cellular process mediating smooth muscle contraction. 1-7 A pool of globular actin (G-actin) is stimulated onto filamentous actin (F-actin) in a variety of smooth muscle cells and tissues in response to agonist stimulation. Blockage of actin polymerization by the inhibitors cytochalasin and latrunculin attenuates active force on activation with contractile stimuli whereas myosin regulatory light chain phosphorylation (MRLCP) is not disrupted. 5,8 -10 These studies suggest that actin dynamics and MRLCP are independently regulated, and that both dynamic changes in the actin cytoskeleton and myosin activation are required for force development during contractile stimulation of smooth muscle. 4,8 -11 However, the mechanisms that regulate the actin cytoskeleton in smooth muscle are not completely understood.The tyrosine phosphorylated protein Crk-associated substrate (CAS) has been implicated in the modulation of the actin cytoskeleton in smooth muscle cells as well as in nonmuscle cells including COS-7 cells and NIH3T3 cells. 9,12-14 Downregulation of CAS by antisense dramatically attenu...

The intermediate filament protein vimentin has been shown to be required for smooth muscle contraction. The adapter protein p130 Crk-associated substrate (CAS) participates in the signaling processes that regulate force development in smooth muscle. However, the interaction of vimentin filaments with CAS has not been well elucidated. In the present study, stimulation of tracheal smooth muscle strips with acetylcholine (ACh) resulted in the increase in ratios of soluble vimentin to insoluble vimentin (an index of vimentin disassembly) in association with force development. Activation with ACh also induced vimentin phosphorylation at Ser-56 as assessed by immunoblot analysis. More importantly, CAS was found in the cytoskeletal vimentin fraction, and the amount of CAS in cytoskeletal vimentin was reduced in smooth muscle strips upon contractile stimulation. CAS redistributed from the myoplasm to the periphery during ACh activation of smooth muscle cells. The decrease in distribution of CAS in cytoskeletal vimentin elicited by ACh was attenuated by the downregulation of p21-activated kinase (PAK) 1 with antisense oligodeoxynucleotides. Vimentin phosphorylation at this residue, the ratio of soluble vimentin to insoluble vimentin, and active force in smooth muscle strips induced by ACh were also reduced in PAK-depleted tissues. These results suggest that PAK may regulate CAS release from the vimentin intermediate filaments by mediating vimentin phosphorylation at Ser-56 and the transition of cytoskeletal vimentin to soluble vimentin. The PAK-mediated the dissociation of CAS from the vimentin network may participate in the cellular processes that affect active force development during acetylcholine activation of tracheal smooth muscle tissues.

This study examined whether elevated intravascular pressure stimulates asynchronous Ca 2+waves in cerebral arterial smooth muscle cells and if their generation contributes to myogenic tone development. The endothelium was removed from rat cerebral arteries, which were then mounted in an arteriograph, pressurized (20-100 mmHg) and examined under a variety of experimental conditions. Diameter and membrane potential (V M ) were monitored using conventional

In this article, we review the literature regarding the role of c-Jun N-terminal kinases (JNKs) in cerebral and myocardial ischemia/reperfusion injury. Numerous studies demonstrate that JNK-mediated signaling pathways play an essential role in cerebral and myocardial ischemia/reperfusion injury. JNK-associated mechanisms are involved in preconditioning and post-conditioning of the heart and the brain. The literature and our own studies suggest that JNK inhibitors may exert cardioprotective and neuroprotective properties. The effects of modulating the JNK-depending pathways in the brain and the heart are reviewed. Cardioprotective and neuroprotective mechanisms of JNK inhibitors are discussed in detail including synthetic small molecule inhibitors (AS601245, SP600125, IQ-1S, and SR-3306), ion channel inhibitor GsMTx4, JNK-interacting proteins, inhibitors of mixed-lineage kinase (MLK) and MLK-interacting proteins, inhibitors of glutamate receptors, nitric oxide (NO) donors, and anesthetics. The role of JNKs in ischemia/reperfusion injury of the heart in diabetes mellitus is discussed in the context of comorbidities. According to reviewed literature, JNKs represent promising therapeutic targets for protection of the brain and the heart against ischemic stroke and myocardial infarction, respectively. However, different members of the JNK family exert diverse physiological properties which may not allow for systemic administration of non-specific JNK inhibitors for therapeutic purposes. Currently available candidate JNK inhibitors with high therapeutic potential are identified. The further search for selective JNK3 inhibitors remains an important task.

This article reviews the existing knowledge about the effects of physical exercise on nitric oxide (NO) production in the cardiopulmonary system. The authors review the sources of NO in the cardiopulmonary system; involvement of three forms of NO synthases (eNOS, nNOS, and iNOS) in exercise physiology; exercise-induced modulation of NO and/or NOS in physiological and pathophysiological conditions in human subjects and animal models in the absence and presence of pharmacological modulators; and significance of exercise-induced NO production in health and disease. The authors suggest that physical activity significantly improves functioning of the cardiovascular system through an increase in NO bioavailability, potentiation of antioxidant defense, and decrease in the expression of reactive oxygen species-forming enzymes. Regular physical exercises are considered a useful approach to treat cardiovascular diseases. Future studies should focus on detailed identification of (i) the exercise-mediated mechanisms of NO exchange; (ii) optimal exercise approaches to improve cardiovascular function in health and disease; and (iii) physical effort thresholds.