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 Protein kinase A activates protein phosphatase 2A by phosphorylation of the B56  subunit

2007 ◽  
Vol 104 (8) ◽  
pp. 2979-2984 ◽  
Author(s):  
J.-H. Ahn ◽  
T. McAvoy ◽  
S. V. Rakhilin ◽  
A. Nishi ◽  
P. Greengard ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Phosphatase 2A ◽  
Kinase A

scholarly journals Protein Kinase C Controls Binding of Igo/ENSA Proteins to Protein Phosphatase 2A in Budding Yeast

2017 ◽  
Vol 292 (12) ◽  
pp. 4925-4941 ◽  
Author(s):  
Vu Thai ◽  
Noah Dephoure ◽  
Amit Weiss ◽  
Jacqueline Ferguson ◽  
Ricardo Leitao ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Protein Phosphatase ◽  
Budding Yeast ◽  
Protein Phosphatase 2A ◽  
Kinase C ◽  
Phosphatase 2A

scholarly journals B56α/Protein Phosphatase 2A Inhibits Adipose Lipolysis in High-Fat Diet-Induced Obese Mice

Endocrinology ◽  
2010 ◽  
Vol 151 (8) ◽  
pp. 3624-3632 ◽  
Author(s):  
Brice P. Kinney ◽  
Liping Qiao ◽  
Justin M. LeVaugh ◽  
Jianhua Shao
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Protein Phosphatase ◽  
High Fat Diet ◽  
Protein Phosphatase 2A ◽  
High Fat ◽  
Protein Levels ◽  
Epididymal Fat ◽  
Phosphatase 2A ◽  
Kinase A

Lipolysis and lipogenesis are two opposite processes that control lipid storage in adipocytes. Impaired adipose lipolysis has been observed in both obese human subjects and animal models. This study investigated the mechanisms underlying impaired adipose lipolysis in a high-fat diet-induced obese (DIO) mouse model. DIO models were created using male C57BL/6 mice. Our results show that β3 adrenergic receptor-specific agonist BRL37344 induced adipose lipolysis was significantly blunted in DIO mice. The levels of Ser660 phosphorylation of hormone-sensitive lipase (HSL) were significantly decreased in the epididymal fat of DIO mice. However, protein levels of HSL, adipose triglyceride lipase and its coactivator comparative gene identification-58 were similar between DIO and control mice. It is known that upon lipolytic hormone stimulation, protein kinase A phosphorylates HSL Ser660 and activates HSL, whereas protein phosphatase 2A (PP2A) dephosphorylates and inactivates HSL. Interestingly, our study shows that high-fat feeding did not alter epididymal fat cAMP and protein kinase A protein levels but significantly increased the expression of the α-isoform of PP2A regulatory subunit B′ (B56α). To study the role of B56α in obesity-associated lipolytic defect, B56α was overexpressed or knocked down by adenovirus-mediated gene transduction in cultured 3T3-L1CARΔ1 adipocytes. Overexpression of B56α significantly decreased HSL Ser660 phosphorylation. In contrast, knocking down B56α increased hormone-stimulated HSL activation and lipolysis in mature 3T3-L1CARΔ1 adipocytes. These results strongly suggest that elevated B56α/PP2A inhibits HSL and lipolysis in white adipose tissue of DIO mice.

Sealing effects of (−)-epigallocatechin gallate on protein kinase C and protein phosphatase 2A

1997 ◽  
Vol 65 (2-3) ◽  
pp. 157-164 ◽  
Author(s):  
Katsuhisa Kitano ◽  
Ki-Youl Nam ◽  
Shunsaku Kimura ◽  
Hirota Fujiki ◽  
Yukio Imanishi
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Epigallocatechin Gallate ◽  
Kinase C ◽  
Phosphatase 2A

scholarly journals Persistent Activation of RelA by Respiratory Syncytial Virus Involves Protein Kinase C, Underphosphorylated IκBβ, and Sequestration of Protein Phosphatase 2A by the Viral Phosphoprotein

1998 ◽  
Vol 72 (7) ◽  
pp. 5610-5618 ◽  
Author(s):  
Vira Bitko ◽  
Sailen Barik
Keyword(s):  
Protein Kinase C ◽  
Respiratory Syncytial Virus ◽  
Protein Kinase ◽  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Oxygen Intermediates ◽  
Kinase C ◽  
Phosphatase 2A ◽  
Initial Activation ◽  
Syncytial Virus

ABSTRACT Respiratory syncytial virus (RSV) activated the RelA (p65) subunit of nuclear factor kappa B (NF-κB) over many hours postinfection. The initial activation coincided with phosphorylation and degradation of IκBα, the cytoplasmic inhibitor of RelA. During persistent activation of NF-κB at later times in infection, syntheses of inhibitors IκBα as well as IκBβ were restored. However, the resynthesized IκBβ was in an underphosphorylated state, which apparently prevented inhibition of NF-κB. Use of specific inhibitors suggested that the pathway leading to the persistent—but not the initial—activation of NF-κB involved signaling through protein kinase C (PKC) and reactive oxygen intermediates of nonmitochondrial origin, whereas phospholipase C or D played little or no role. Thus, RSV infection led to the activation of NF-κB by a biphasic mechanism: a transient or early activation involving phosphorylation of the inhibitor IκB polypeptides, and a persistent or long-term activation requiring PKC and the generation of hypophosphorylated IκBβ. At least a part of the activation was through a novel mechanism in which the viral phosphoprotein P associated with but was not dephosphorylated by protein phosphatase 2A and thus sequestered and inhibited the latter. We postulate that this led to a net increase in the phosphorylation state of signaling proteins that are responsible for RelA activation.

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