Protein serine/threonine phosphatases; an expanding family

Cohen, Patricia T.W.; Brewis, Neil; Hughes, Valerie; Mann, David J.

doi:10.1016/0014-5793(90)81285-v

Cited by 230 publications

(136 citation statements)

References 29 publications

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“…For example, Protein Phosphatase 2A (PP2A) is a major intracellular serine/ threonine phosphatase that, apart from being involved in cell cycle regulation, plays a role in diverse cellular processes such as DNA-replication, intermediary metabolism, transcription and signal transduction (Hubbard and Cohen, 1993;Mumby and Walter, 1993;Virshup et al, 1993;Mayer-Jaekel and Hemmings, 1994). PP2A consists of a catalytic subunit (PP2Ac) (Cohen et al, 1990) and a structural 65 kDa subunit (PR65) (Hemmings et al, 1990). These two proteins form a core dimer (Hendrix et al, 1993b) to which various other regulatory`B' subunits associate.…”

Section: Introductionmentioning

confidence: 99%

Functional interaction between a novel protein phosphatase 2A regulatory subunit, PR59, and the retinoblastoma-related p107 protein

1999

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The proteins of the retinoblastoma family are potent inhibitors of cell cycle progression. It is well documented that their growth-inhibitory activity can be abolished by phosphorylation on serine and threonine residues by cyclin dependent kinases. In contrast, very little is known about the dephosphorylation of retinoblastoma-family proteins. We report here the isolation, by virtue of its ability to associate with p107, of a novel Protein Phosphatase 2A (PP2A) regulatory subunit, named PR59. PR59 shares sequence homology with a known regulatory subunit of PP2A, PR72, but di ers from PR72 in its expression pattern and its functional properties. We show that PR59 co-immunoprecipitates with the PP2A catalytic subunit, indicating that PR59 is a genuine component of PP2A holo-enzymes. In vivo, PR59 associates speci®cally with p107, but not with pRb. Elevated expression of PR59 results in dephosphorylation of p107, but not of pRb, and inhibits cell proliferation by causing cells to accumulate in G1. These data support a model in which the distinct PP2A regulatory subunits act to target the PP2A catalytic subunit to speci®c substrates and suggest a role for PP2A in regulation of p107.

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Section: Introductionmentioning

confidence: 99%

Functional interaction between a novel protein phosphatase 2A regulatory subunit, PR59, and the retinoblastoma-related p107 protein

1999

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“…Protein phosphatase type 1 (PP1) is a family of serine/threonine protein phosphatases (PPs) that are sensitive to heat-stable inhibitory proteins unlike the other known PPs, PP2A, PP2B, and PP2C [3]. The cDNAs encoding the catalytic subunit of PP1 were isolated from yeast, rabbit, and mouse [4]. Four distinct cDNA clones for rat PP1 catalytic subunits have been isolated from rat tissues and designated as PPla, PP1y1, PPI~2, and PP18 [5].…”

Section: Introductionmentioning

confidence: 99%

Immunohistochemical and immunoblotting identification of protein phosphatase 1γ1 in rat salivary glands

Shirakawa¹,

Mochizuki²,

Kobayashi³

et al. 1996

FEBS Letters

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We have analyzed the distribution of the ~1 isotype of rat protein phosphatase type 1 catalytic subunit in rat salivary glands. Formaldehyde-fixed paraffin sections were reacted with the PP1T1 antibody using an immunohistochemical method. Positive staining occurred in striated ducts of parotid gland. However, the staining reaction was less intense in submandibular gland. Proteins were also prepared from rat salivary glands and subjected to SDS-PAGE, followed by Western blotting analysis with the PP171 antibody. The antibody interacted with protein corresponding to an estimated molecular mass of 36 kDa present in the parotid gland. The staining reaction was considerably weaker with the proteins from submandibular gland.

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“…Various molecular biology techniques have led to the identification of several additional phosphatases including protein phosphatase 4, formerly known as protein phosphatase X (7,8).…”

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Purification and Identification of a Novel Subunit of Protein Serine/Threonine Phosphatase 4

Kloeker¹,

Wadzinski

1999

Journal of Biological Chemistry

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The catalytic subunit of protein serine/threonine phosphatase 4 (PP4 C ) has greater than 65% amino acid identity to the catalytic subunit of protein phosphatase 2A (PP2A C ). Despite this high homology, PP4 does not appear to associate with known PP2A regulatory subunits. As a first step toward characterization of PP4 holoenzymes and identification of putative PP4 regulatory subunits, PP4 was purified from bovine testis soluble extracts. PP4 existed in two complexes of approximately 270 -300 and 400 -450 kDa as determined by gel filtration chromatography. The smaller PP4 complex was purified by sequential phenyl-Sepharose, Source 15Q, DEAE2, and Superdex 200 gel filtration chromatographies. The final product contained two major proteins: the PP4 catalytic subunit plus a protein that migrated as a doublet of 120 -125 kDa on SDS-polyacrylamide gel electrophoresis. The associated protein, termed PP4 R1 , and PP4 C also bound to microcystinSepharose. Mass spectrometry analysis of the purified complex revealed two major peaks, at 35 (PP4 C ) and 105 kDa (PP4 R1 ). Amino acid sequence information of several peptides derived from the 105 kDa protein was utilized to isolate a human cDNA clone. Analysis of the predicted amino acid sequence revealed 13 nonidentical repeats similar to repeats found in the A subunit of PP2A (PP2A A ). The PP4 R1 cDNA clone engineered with an N-terminal Myc tag was expressed in COS M6 cells and PP4 C co-immunoprecipitated with Myc-tagged PP4 R1 . These data indicate that one form of PP4 is similar to the core complex of PP2A in that it consists of a catalytic subunit and a "PP2A A -like" structural subunit.

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Protein serine/threonine phosphatases; an expanding family

Cited by 230 publications

References 29 publications

Functional interaction between a novel protein phosphatase 2A regulatory subunit, PR59, and the retinoblastoma-related p107 protein

Functional interaction between a novel protein phosphatase 2A regulatory subunit, PR59, and the retinoblastoma-related p107 protein

Immunohistochemical and immunoblotting identification of protein phosphatase 1γ1 in rat salivary glands

Purification and Identification of a Novel Subunit of Protein Serine/Threonine Phosphatase 4

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