scholarly journals CK1 activates minus-end–directed transport of membrane organelles along microtubules

2011 ◽  
Vol 22 (8) ◽  
pp. 1321-1329 ◽  
Author(s):  
Kazuho Ikeda ◽  
Olga Zhapparova ◽  
Ilya Brodsky ◽  
Irina Semenova ◽  
Jennifer S. Tirnauer ◽  
...  
Keyword(s):  
Protein Phosphatase ◽  
Pigment Granule ◽  
Organelle Transport ◽  
Signaling Mechanism ◽  
Pigment Granules ◽  
Dynein Motor ◽  
Dynein Intermediate Chain ◽  
Phosphatase 2A ◽  
Pigment Aggregation ◽  
Rapid Activation

Microtubule (MT)-based organelle transport is driven by MT motor proteins that move cargoes toward MT minus-ends clustered in the cell center (dyneins) or plus-ends extended to the periphery (kinesins). Cells are able to rapidly switch the direction of transport in response to external cues, but the signaling events that control switching remain poorly understood. Here, we examined the signaling mechanism responsible for the rapid activation of dynein-dependent MT minus-end–directed pigment granule movement in Xenopus melanophores (pigment aggregation). We found that, along with the previously identified protein phosphatase 2A (PP2A), pigment aggregation signaling also involved casein kinase 1ε (CK1ε), that both enzymes were bound to pigment granules, and that their activities were increased during pigment aggregation. Furthermore we found that CK1ε functioned downstream of PP2A in the pigment aggregation signaling pathway. Finally, we discovered that stimulation of pigment aggregation increased phosphorylation of dynein intermediate chain (DIC) and that this increase was partially suppressed by CK1ε inhibition. We propose that signal transduction during pigment aggregation involves successive activation of PP2A and CK1ε and CK1ε-dependent phosphorylation of DIC, which stimulates dynein motor activity and increases minus-end–directed runs of pigment granules.

scholarly journals Protein kinase C activation antagonizes melatonin-induced pigment aggregation in Xenopus laevis melanophores.

1992 ◽  
Vol 119 (6) ◽  
pp. 1515-1521 ◽  
Author(s):  
D Sugden ◽  
S J Rowe
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Xenopus Laevis ◽  
Pigment Granule ◽  
Melatonin Receptors ◽  
Kinase C ◽  
Pigment Granules ◽  
Slow Aggregation ◽  
Pigment Aggregation ◽  
Induced Aggregation

The pineal hormone, melatonin (5-methoxy N-acetyltryptamine) induces a rapid aggregation of melanin-containing pigment granules in isolated melanophores of Xenopus laevis. Treatment of melanophores with activators of protein kinase C (PKC), including phorbol esters, mezerein and a synthetic diacylglycerol, did not affect pigment granule distribution but did prevent and reverse melatonin-induced pigment aggregation. This effect was blocked by an inhibitor of PKC, Ro 31-8220. The inhibitory effect was not a direct effect on melatonin receptors, per se, as the slow aggregation induced by a high concentration of an inhibitor of cyclic AMP-dependent protein kinase (PKA), adenosine 3',5'-cyclic monophosphothioate, Rp-diastereomer (Rp-cAMPS), was also reversed by PKC activation. Presumably activation of PKC, like PKA activation, stimulates the intracellular machinery involved in the centrifugal translocation of pigment granules along microtubules. alpha-Melanocyte stimulating hormone (alpha-MSH), like PKC activators, overcame melatonin-induced aggregation but this response was not blocked by the PKC inhibitor, Ro 31-8220. This data indicates that centrifugal translocation (dispersion) of pigment granules in Xenopus melanophores can be triggered by activation of either PKA, as occurs after alpha-MSH treatment, or PKC. The very slow aggregation in response to inhibition of PKA with high concentrations of Rp-cAMPS, suggests that the rapid aggregation in response to melatonin may involve multiple intracellular signals in addition to the documented Gi-mediated inhibition of adenylate cyclase.

scholarly journals Dynein, Dynactin, and Kinesin II's Interaction with Microtubules Is Regulated during Bidirectional Organelle Transport

2000 ◽  
Vol 151 (1) ◽  
pp. 155-166 ◽  
Author(s):  
Eric L. Reese ◽  
Leah T. Haimo
Keyword(s):  
Pigment Granule ◽  
Cytoplasmic Dynein ◽  
Binding Activity ◽  
The State ◽  
Organelle Transport ◽  
Microtubule Binding ◽  
Pigment Granules ◽  
Microtubule Motors

The microtubule motors, cytoplasmic dynein and kinesin II, drive pigmented organelles in opposite directions in Xenopus melanophores, but the mechanism by which these or other motors are regulated to control the direction of organelle transport has not been previously elucidated. We find that cytoplasmic dynein, dynactin, and kinesin II remain on pigment granules during aggregation and dispersion in melanophores, indicating that control of direction is not mediated by a cyclic association of motors with these organelles. However, the ability of dynein, dynactin, and kinesin II to bind to microtubules varies as a function of the state of aggregation or dispersion of the pigment in the cells from which these molecules are isolated. Dynein and dynactin bind to microtubules when obtained from cells with aggregated pigment, whereas kinesin II binds to microtubules when obtained from cells with dispersed pigment. Moreover, the microtubule binding activity of these motors/dynactin can be reversed in vitro by the kinases and phosphatase that regulate the direction of pigment granule transport in vivo. These findings suggest that phosphorylation controls the direction of pigment granule transport by altering the ability of dynein, dynactin, and kinesin II to interact with microtubules.

scholarly journals Regulation of organelle transport in melanophores by calcineurin.

1990 ◽  
Vol 111 (5) ◽  
pp. 1939-1948 ◽  
Author(s):  
C D Thaler ◽  
L T Haimo
Keyword(s):  
Protein Phosphorylation ◽  
Phosphatase Activity ◽  
Okadaic Acid ◽  
Pigment Granule ◽  
Retrograde Transport ◽  
Organelle Transport ◽  
Calmodulin Antagonists ◽  
Activity Inhibition ◽  
Pigment Aggregation ◽  
Calcineurin Activity

Previous studies have shown that pigment granule dispersion and aggregation in melanophores of the African cichlid, Tilapia mossambica, are regulated by protein phosphorylation and dephosphorylation, respectively (Rozdzial, M. M., and L. T. Haimo. 1986. Cell. 47:1061-1070). The present studies suggest that calcineurin, a Ca2+/calmodulin-stimulated phosphatase, is the endogenous phosphatase that mediates pigment aggregation in melanophores. Aggregation, but not dispersion, is inhibited by okadaic acid at concentrations consistent with an inhibition of calcineurin activity. Inhibition of aggregation in melanophores that have been BAPTA loaded or treated with calmodulin antagonists implicate Ca2+ and calmodulin, respectively, in this process. Moreover, addition of calcineurin rescues aggregation in lysed melanophores which are otherwise incapable of aggregating pigment. Immunoblotting with an anticalcineurin IgG reveals that calcineurin is a component of the dermis, which contains the melanophores, and indirect immunofluorescence localizes calcineurin specifically to the melanophores. Finally, this antibody, which inhibits calcineurin's phosphatase activity (Tash, J. S., M. Krinks, J. Patel, R. L. Means, C. B. Klee, and A. R. Means. 1988. J. Cell Biol. 106:1625-1633), inhibits aggregation but has no effect on pigment granule dispersion. Together these studies indicate that retrograde transport of pigment granules to the melanophore cell center depends upon the participation of calcineurin.

scholarly journals Regulation of Mih1/Cdc25 by protein phosphatase 2A and casein kinase 1

2008 ◽  
Vol 180 (5) ◽  
pp. 931-945 ◽  
Author(s):  
Gayatri Pal ◽  
Maria T.Z. Paraz ◽  
Douglas R. Kellogg
Keyword(s):  
Cell Cycle ◽  
Protein Phosphatase ◽  
Feedback Loop ◽  
Cell Cycle Progression ◽  
Protein Phosphatase 2A ◽  
Casein Kinase ◽  
Cycle Progression ◽  
Signaling Mechanism ◽  
Casein Kinase 1 ◽  
Phosphatase 2A

The Cdc25 phosphatase promotes entry into mitosis by removing cyclin-dependent kinase 1 (Cdk1) inhibitory phosphorylation. Previous work suggested that Cdc25 is activated by Cdk1 in a positive feedback loop promoting entry into mitosis; however, it has remained unclear how the feedback loop is initiated. To learn more about the mechanisms that regulate entry into mitosis, we have characterized the function and regulation of Mih1, the budding yeast homologue of Cdc25. We found that Mih1 is hyperphosphorylated early in the cell cycle and is dephosphorylated as cells enter mitosis. Casein kinase 1 is responsible for most of the hyperphosphorylation of Mih1, whereas protein phosphatase 2A associated with Cdc55 dephosphorylates Mih1. Cdk1 appears to directly phosphorylate Mih1 and is required for initiation of Mih1 dephosphorylation as cells enter mitosis. Collectively, these observations suggest that Mih1 regulation is achieved by a balance of opposing kinase and phosphatase activities. Because casein kinase 1 is associated with sites of polar growth, it may regulate Mih1 as part of a signaling mechanism that links successful completion of growth-related events to cell cycle progression.

scholarly journals Regulation of Organelle Movement in Melanophores by Protein Kinase A (PKA), Protein Kinase C (PKC), and Protein Phosphatase 2A (PP2A)

1998 ◽  
Vol 142 (3) ◽  
pp. 803-813 ◽  
Author(s):  
Amy R. Reilein ◽  
Irina S. Tint ◽  
Natalia I. Peunova ◽  
Grigori N. Enikolopov ◽  
Vladimir I. Gelfand
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Protein Kinase A ◽  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Organelle Transport ◽  
Pigment Dispersion ◽  
Kinase C ◽  
Phosphatase 2A ◽  
Kinase A

We used melanophores, cells specialized for regulated organelle transport, to study signaling pathways involved in the regulation of transport. We transfected immortalized Xenopus melanophores with plasmids encoding epitope-tagged inhibitors of protein phosphatases and protein kinases or control plasmids encoding inactive analogues of these inhibitors. Expression of a recombinant inhibitor of protein kinase A (PKA) results in spontaneous pigment aggregation. α-Melanocyte-stimulating hormone (MSH), a stimulus which increases intracellular cAMP, cannot disperse pigment in these cells. However, melanosomes in these cells can be partially dispersed by PMA, an activator of protein kinase C (PKC). When a recombinant inhibitor of PKC is expressed in melanophores, PMA-induced pigment dispersion is inhibited, but not dispersion induced by MSH. We conclude that PKA and PKC activate two different pathways for melanosome dispersion. When melanophores express the small t antigen of SV-40 virus, a specific inhibitor of protein phosphatase 2A (PP2A), aggregation is completely prevented. Conversely, overexpression of PP2A inhibits pigment dispersion by MSH. Inhibitors of protein phosphatase 1 and protein phosphatase 2B (PP2B) do not affect pigment movement. Therefore, melanosome aggregation is mediated by PP2A.

scholarly journals Novel bradykinin signaling in adult rat cardiac myocytes through activation of p21-activated kinase

2010 ◽  
Vol 298 (4) ◽  
pp. H1283-H1289 ◽  
Author(s):  
Yunbo Ke ◽  
Katherine A. Sheehan ◽  
E. Eroume A. Egom ◽  
Ming Lei ◽  
R. John Solaro
Keyword(s):  
Cardiac Myocytes ◽  
Protein Phosphatase ◽  
Intracellular Signaling ◽  
Troponin I ◽  
Protein Phosphatase 2A ◽  
Signaling Mechanism ◽  
Adult Rat ◽  
Phosphatase 2A ◽  
P21 Activated Kinase ◽  
Rat Cardiac Myocytes

Although bradykinin (BK) is known to exert effects on the myocardium, its intracellular signaling pathways remain poorly understood. Experiments in other cell types indicated that p21-activated kinase-1 (Pak1), a Ser/Thr kinase downstream of small monomeric G proteins, is activated by BK. We previously reported that the expression of active Pak1 in adult cardiac myocytes induced activation of protein phosphatase 2A and dephosphorylation of myofilament proteins (Ke et al. Circ Res 94: 194–200, 2004). In experiments reported here, we tested the hypothesis that BK signals altered protein phosphorylation in adult rat cardiac myocytes through the activation and translocation of Pak1. Treatment of myocytes with BK resulted in the activation of Pak1 as demonstrated by increased autophosphorylation at Thr423 and a diminished striated localization, which is present in the basal state. BK induced dephosphorylation of both cardiac troponin I and phospholamban. Treatment of isolated myocytes with BK also blunted the effect of isoproterenol to enhance peak Ca2+ and relaxation of Ca2+ transients. Protein phosphatase 2A was demonstrated to associate with both Pak 1 and phospholamban. Our studies indicate a novel signaling mechanism for BK in adult rat cardiac myocytes and support our hypothesis that Pak 1 is a significant regulator of phosphatase activity in the heart.

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