Phosphorylation of caldesmon by mitogen‐activated protein kinase with no effect on Ca2+ sensitivity in rabbit smooth muscle.

Nixon, Graeme F.; Iizuka, Kunihiko; Haystead, Clare M.M.; Haystead, Timothy; Somlyo, Andrew P.; Somlyo, Avril V.

doi:10.1113/jphysiol.1995.sp020879

Cited by 73 publications

(62 citation statements)

References 21 publications

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“…In the image of Erk-phosphorylated H32K the density over subdomain 1 is much less and the inter-strand connectivity is lost. These results are Although demonstrated by the in vitro experiments, the regulatory role of h-CaD phosphorylation by MAPK in smooth muscle cells still remains controversial, primarily because inhibition of MAPK failed to produce detectable differences in contractility of smooth muscle tissues [47]. On the other hand, there is little doubt that phosphorylation of l-CaD is involved in non-muscle cell division and locomotion.…”

Section: +mentioning

confidence: 49%

Phosphorylation of caldesmon during smooth muscle contraction and cell migration or proliferation

2006

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SummaryThe actin-binding protein caldesmon (CaD) exists both in smooth muscle (the heavy isoform, h-CaD) and non-muscle cells (the light isoform, l-CaD). In smooth muscles h-CaD binds to myosin and actin simultaneously and modulates the actomyosin interaction. In non-muscle cells l-CaD binds to actin and stabilizes the actin stress fibers; it may also mediate the interaction between actin and non-muscle myosins. Both h-and l-CaD are phosphorylated in vivo upon stimulation. The major phosphorylation sites of h-CaD when activated by phorbol ester are the Erk-specific sites, modification of which is attenuated by the MEK inhibitor PD98059. The same sites in l-CaD are also phosphorylated when cells are stimulated to migrate, whereas in dividing cells l-CaD is phosphorylated more extensively, presumably by cdc2 kinase. Both Erk and cdc2 are members of the MAPK family. Thus it appears that CaD is a downstream effector of the Ras signaling pathways. Significantly, the phosphorylatable serine residues shared by both CaD isoforms are in the C-terminal region that also contains the actin-binding sites. Biochemical and structural studies indicated that phosphorylation of CaD at the Erk sites is accompanied by a conformational change that partially dissociates CaD from actin. Such a structural change in h-CaD exposes the myosin-binding sites on the actin surface and allows actomyosin interactions in smooth muscles. In the case of non-muscle cells, the change in l-CaD weakens the stability of the actin filament and facilitates its disassembly. Indeed, the level of l-CaD modification correlates very well in a reciprocal manner with the level of actin stress fibers. Since both cell migration and cell division require dynamic remodeling of actin cytoskeleton that leads to cell shape changes, phosphorylation of CaD may therefore serve as a plausible means to regulate these processes. Thus CaD not only links the smooth muscle contractility and non-muscle motility, but also provides a common mechanism for the regulation of cell migration and cell proliferation.Abbreviations: BPM -benzophenone maleimide; CaD -caldesmon; CaM -calmodulin; EM -electron microscopy; Erk -extracellular signal-regulated kinase; FRET -fluorescence resonance energy transfer; GFP -green fluorescent protein; h-CaD -smooth muscle caldesmon; IAEDANS -5-(iodoacetamidoethyl) aminonaphthalene-1-sulfonic acid; l-CaD -non-muscle caldesmon; MAPK -mitogen activated protein kinase; MLCK -myosin light chain kinase; MS -mass spectrometry; Pak -p21-activated protein kinase; PMA -phorbol 12-myristate 13-acetate; Raf -rat aorta fibroblast cells; Tm -tropomyosin Remodeling of actin cytoskeleton plays a central role in a variety of cellular processes that involve shape change and movement. Malfunction of these processes could lead to pathological consequences, but how actin-mediated motility is regulated is only beginning to be understood. With recent

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confidence: 49%

Phosphorylation of caldesmon during smooth muscle contraction and cell migration or proliferation

2006

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“…Similarly, the addition of ERK1 to permeabilized canine colonic smooth muscle contracted the muscle (7). However, in permeabilized rabbit vascular smooth muscle, phosphorylation of CaD by constitutively activated ERK2 neither induced contraction nor affected the calcium sensitivity (28). Thus the effects of ERK1/2 on CaD may be isoform specific, tissue, or species specific.…”

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confidence: 87%

ERK1/2-mediated phosphorylation of myometrial caldesmon during pregnancy and labor

Malek³

et al. 2003

American Journal of Physiology-Regulatory, Integrative and Comp

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“…18 and 34). Although the thin filament protein calponin has received some attention (14,31), by far the majority of experimentation has been aimed at a potential role for caldesmon (4,7,23,26,38). Both proteins inhibit actin-activated myosin ATPase activity, and this inhibition is reversed by high levels of Ca 2ϩ and calmodulin or by phosphorylation.…”

Section: Discussionmentioning

confidence: 99%

siRNA knock down of casein kinase 2 increases force and cross-bridge cycling rates in vascular smooth muscle

Smolock

Wang²,

Nolt³

et al. 2007

American Journal of Physiology-Cell Physiology

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Smolock EM, Wang T, Nolt JK, Moreland RS. siRNA knock down of casein kinase 2 increases force and cross-bridge cycling rates in vascular smooth muscle. Am J Physiol Cell Physiol 292: C876-C885, 2007. First published September 20, 2006; doi:10.1152/ajpcell.00343.2006.-Contraction of smooth muscle involves myosin light chain (MLC) kinase catalyzed phosphorylation of the regulatory MLC, activation of myosin, and the development of force. However, this cannot account for all aspects of a smooth muscle contraction, suggesting that other regulatory mechanisms exist. One potentially important technique to study alternative sites of contractile regulation is the use of small interfering RNA (siRNA). The goal of this study was to determine whether siRNA technology can decrease the levels of a specific protein and allow for the determination of how that protein affects contractile regulation. To achieve this goal, we tested the hypothesis that casein kinase 2 (CK2) is part of the complex regulatory scheme present in vascular smooth muscle. Using intact strips of swine carotid artery, we determined that siRNA against CK2 produced a tissue that resulted in a ϳ60% knockdown after 4 days in organ culture. Intact strips of vascular tissue depleted of CK2 produced greater levels of force and exhibited an increased sensitivity to all stimuli tested. This was accompanied by an increase in crossbridge cycling rates but not by a change in MLC phosphorylation levels. ␣-Toxin-permeabilized vascular tissue depleted of CK2 also showed an increased sensitivity to calcium compared with control tissues. Our results demonstrate that siRNA is a viable technique with which to study regulatory pathways in intact smooth muscle tissue. Our results also demonstrate that CK2 plays an important role in the mechanism(s) responsible for the development of force and crossbridge cycling by a MLC phosphorylation-independent pathway. myosin light chain phosphorylation; shortening velocity; ␣-toxin permeabilization; swine carotid artery; caldesmon THE PRIMARY PATHWAY for the initiation of a vascular smooth muscle contraction involves Ca 2ϩ -calmodulin-dependent myosin light chain (MLC) kinase catalyzed phosphorylation of the Ser 19 residue on the 20-kDa MLC (22). However, this cascade of cellular events cannot account for all known properties of smooth muscle contractile regulation. For example, the tonic maintenance of force is not supported by proportional levels of MLC phosphorylation (37), near-maximal levels of force can be developed in the complete absence of an increase in levels of MLC phosphorylation (8, 49), and loss or displacement of the thin filament protein, caldesmon, produces stimulationindependent, active cross-bridge cycling (7,23). Results such as these have drawn attention to other potential mechanisms for the regulation, or at least the modulation, of smooth muscle contraction. In particular, proteins associated with the thin filaments of smooth muscle have been targeted for study.The two most widely studied thin filament proteins a...

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Phosphorylation of caldesmon by mitogen‐activated protein kinase with no effect on Ca2+ sensitivity in rabbit smooth muscle.

Cited by 73 publications

References 21 publications

Phosphorylation of caldesmon during smooth muscle contraction and cell migration or proliferation

Phosphorylation of caldesmon during smooth muscle contraction and cell migration or proliferation

ERK1/2-mediated phosphorylation of myometrial caldesmon during pregnancy and labor

siRNA knock down of casein kinase 2 increases force and cross-bridge cycling rates in vascular smooth muscle

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