Faculty Opinions recommendation of Protein kinase A activates protein phosphatase 2A by phosphorylation of the B56delta subunit.

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.

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Protein Phosphatase 2A Is Involved in the Regulation of Protein Kinase A Signaling Pathway during in Vitro Chondrogenesis

Experimental Cell Research ◽

10.1006/excr.2002.5487 ◽

2002 ◽

Vol 275 (1) ◽

pp. 1-8 ◽

Cited By ~ 33

Author(s):

Róza Zákány ◽

Kornélia Szűcs ◽

Éva Bakó ◽

Szabolcs Felszeghy ◽

Gabriella Czifra ◽

...

Keyword(s):

Protein Kinase ◽

Protein Kinase A ◽

Signaling Pathway ◽

Protein Phosphatase ◽

Protein Phosphatase 2A ◽

Phosphatase 2A ◽

Kinase A

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Aberrant glycosylation modulates phosphorylation of tau by protein kinase A and dephosphorylation of tau by protein phosphatase 2A and 5

Neuroscience ◽

10.1016/s0306-4522(02)00510-9 ◽

2002 ◽

Vol 115 (3) ◽

pp. 829-837 ◽

Cited By ~ 64

Author(s):

F Liu ◽

T Zaidi ◽

K Iqbal ◽

I Grundke-Iqbal ◽

C.-X Gong

Keyword(s):

Protein Kinase ◽

Protein Kinase A ◽

Protein Phosphatase ◽

Protein Phosphatase 2A ◽

Aberrant Glycosylation ◽

Phosphatase 2A ◽

Kinase A

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

The Journal of Cell Biology ◽

10.1083/jcb.142.3.803 ◽

1998 ◽

Vol 142 (3) ◽

pp. 803-813 ◽

Cited By ~ 70

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.

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