Molecular cloning of a 74‐kDa regulatory subunit (B″ or δ) of human protein phosphatase 2A

Takahashi, Osamu; Nagase, Terumasa; Murakami, Takehiko; Nozaki, Hideto; Usui, Hirofumi; Nishito, Yasumasa; Hayashi, Hideyuki; Kagamiyama, Hiroyuki; Takeda, Masao

doi:10.1016/0014-5793(95)01500-0

Cited by 52 publications

(60 citation statements)

References 32 publications

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“…Clearly, additional research is needed to further characterize whether PP2A is regulated by other cAMP-dependent mechanisms. The B56␦ subunit exhibits a widespread tissue distribution being found in most tissues examined, with highest levels being found in brain (33,34). The B56␥2 and -␥3 isoforms are also widely distributed (23).…”

Section: Discussionmentioning

confidence: 98%

Protein kinase A activates protein phosphatase 2A by phosphorylation of the B56δ subunit

Ahn

McAvoy

Rakhilin

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

245

242

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Our previous studies of DARPP-32 in striatal slices have shown that activation of D1 receptors leads to cAMP-dependent dephosphorylation of Thr-75, the Cdk5 site in DARPP-32. In the current study, we have elucidated a mechanism whereby protein phosphatase 2A (PP2A) is activated by a cAMP/PKA-dependent pathway, leading to dephosphorylation of Thr-75. PP2A consists of a catalytic C subunit that associates with the scaffolding A subunit and a variety of B subunits. We have found that the A/C subunits of PP2A, in association with the B56␦ (or PPP2R5D) regulatory subunit, is an active DARPP-32 phosphatase. The B56␦ subunit expressed in HEK293 cells forms a heterotrimeric assembly that catalyzes PKA-mediated dephosphorylation at Thr-75 in DARPP-32 (also cotransfected into HEK293 cells). The B56␦ subunit is phosphorylated by PKA, and this increases the overall activity of PP2A in vitro and in vivo. Among four PKA-phosphorylation sites identified in B56␦ in vitro, Ser-566 was found to be critical for the regulation of PP2A activity. Moreover, Ser-566 was phosphorylated by PKA in response to activation of D1 receptors in striatal slices. Based on these studies, we propose that the B56␦/A/C PP2A complex regulates the dephosphorylation of DARPP-32 at Thr-75, thereby helping coordinate the efficacy of dopaminergic neurotransmission in striatal neurons. Moreover, stimulation of protein phosphatase activity by this mechanism may represent an important signaling pathway regulated by cAMP in neurons and other types of cell.cAMP ͉ DARPP-32 ͉ protein phosphorylation D ARPP-32 is a phosphoprotein that is highly enriched in dopaminoceptive medium-sized spiny neurons in the striatum and nucleus accumbens (1, 2). A variety of biochemical studies as well as targeted deletion and mutation of DARPP-32 in mice have shown that DARPP-32 plays a critical role in the actions of dopamine as well as in the actions of antipsychotic drugs, drugs of abuse, and other agents that modulate dopamine levels in the brain (2-5). Through activation of the D1 subclass of receptors, dopamine increases cAMP, activates protein kinase A (PKA), and phosphorylates Thr-34 of DARPP-32. Phosphorylation at Thr-34 converts DARPP-32 into a potent, high-affinity inhibitor of the broad specificity serine/threonine protein phosphatase, PP-1, leading to increased phosphorylation of many physiologically important substrates in medium spiny neurons, including neurotransmitter receptors, voltage-gated ion channels, ion pumps, protein kinases, and transcription factors (1, 2).In addition to Thr-34, DARPP-32 is phosphorylated at multiple sites by several protein kinases, including CK1, CK2 and Cdk5 (6-9). In particular, phosphorylation of Thr-75 by Cdk5 blocks PKA-mediated phosphorylation of Thr-34 of DARPP-32, thereby modulating the efficacy of the dopamine/D1/cAMP/ PKA/DARPP-32/PP1 signaling cascade (8). Our previous studies have found that there is a reciprocal relationship between the phosphorylation status of . Under basal conditions in striatal neurons in vivo or in vit...

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Section: Discussionmentioning

confidence: 98%

Protein kinase A activates protein phosphatase 2A by phosphorylation of the B56δ subunit

Ahn

McAvoy

Rakhilin

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

245

242

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“…The B family has three members, Ba,Bb and Bg, each with a molecular mass of around 55 kDa (Healy et al, 1991;Mayer et al, 1991;Pallas et al, 1992;Zolnierowicz et al, 1994). The B' family consists of numerous isoforms and splice variants whose molecular masses range from 54 ± 68 kDa (Csortos et al, 1996;McCright et al, 1996;McCright and Virshup, 1995;Tanabe et al, 1996;Tehrani et al, 1996). The B'' family has at least four members, designated PR48, PR59, PR72 and PR130 (Hendrix et al, 1993;Nagase et al, 1997;Voorhoeve et al, 1999;Yan et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

Disruption of protein phosphatase 2A subunit interaction in human cancers with mutations in the Aα subunit gene

2001

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“…The B family has four members, Ba, Bb, Bg and Bd, each with a molecular mass of around 55 kDa (Healy et al, 1991;Mayer et al, 1991;Pallas et al, 1992;Strack et al, 1999;Zolnierowicz et al, 1994). The B' family consists of numerous isoforms and splice variants whose molecular masses range from 54 to 68 kDa (Csortos et al, 1996;McCright et al, 1996;McCright and Virshup, 1995;Tanabe et al, 1996;Tehrani et al, 1996). The B'' family has at least four members, designated PR48 (Yan et al, 2000), PR59 (Voorhoeve et al, 1999), and PR72/PR130 (Hendrix et al, 1993;Nagase et al, 1997).…”

Section: Introductionmentioning

confidence: 99%

Alterations in protein phosphatase 2A subunit interaction in human carcinomas of the lung and colon with mutations in the Aβ subunit gene

2001

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Protein phosphatase 2A (PP2A) consists of three subunits, A, B and C. The A and B subunits have regulatory functions while C is the catalytic subunit. PP2A core enzyme is composed of subunits A and C, and the holoenzyme of subunits A, B and C. All subunits exist as multiple isoforms or splice variants. The A subunit exists as two isoforms, Aa and Ab. Here we report about the properties of eight Ab mutants, which were found in human lung and colon cancer. These mutants were reconstructed by site-directed mutagenesis and assayed for their ability to bind B and C subunits. Two mutants showed decreased binding of PR72, a member of the B'' family of B subunits, but normal C subunit binding; two mutants exhibited decreased binding of the C subunit and of B''/PR72; and one mutant showed increased binding of both the C subunit and B''/PR72. Of three mutants that behaved like the wildtype Ab subunit, one is a polymorphic variant and another one is altered outside the binding region for B and C subunits. Importantly, we also found that the wildtype Aa and Ab isoforms, although 85% identical, are remarkably di erent in their ability to bind B and C subunits. Our ®ndings may have important implications in regard to the role of PP2A as a tumor suppressor.

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Molecular cloning of a 74‐kDa regulatory subunit (B″ or δ) of human protein phosphatase 2A

Cited by 52 publications

References 32 publications

Protein kinase A activates protein phosphatase 2A by phosphorylation of the B56δ subunit

Protein kinase A activates protein phosphatase 2A by phosphorylation of the B56δ subunit

Disruption of protein phosphatase 2A subunit interaction in human cancers with mutations in the Aα subunit gene

Alterations in protein phosphatase 2A subunit interaction in human carcinomas of the lung and colon with mutations in the Aβ subunit gene

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