Linked Life Data

14534713

Source:http://linkedlifedata.com/resource/pubmed/id/14534713

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
6
pubmed:dateCreated
2003-10-9
pubmed:abstractText
Reversible serine/threonine protein phosphorylation catalyzed by kinases and phosphatases 2A (PP2A) plays a crucial role in cellular growth and differentiation. We attempted to determine the subcellular location of PP2A in ovarian cancer cells and its regulation by gonadotropin-releasing hormone (GnRH), which is known to have anti-proliferative actions on ovarian cancers. Surgically removed ovarian cancers were screened for GnRH receptor expression prior to subcellular fractionations. PP2A activity was assessed by measuring the dephosphorylation of phosphopeptide highly selective for the PP2A in cytosol and membranes fractionated on a continuous sucrose density gradient. To assess GnRH effects, cloned cell lines were pretreated with or without a GnRH agonist. There were three peaks of PP2A activity, corresponding by marker enzyme analysis to the cytoplasm, plasma membrane and endoplasmic reticulum fractions. The kinetic analysis showed a different activity in cytosol and membrane; Km values for substrate of 185 microM and Vmax of 555 pmol/mg protein/30 min for cytosol, and 28 microM and 83 pmol/mg protein/30 min for plasma membrane, respectively. PP2A-specific inhibitor okadaic acid inhibited the cytosolic and membrane-associated activity by 50% when added at 2 nM and 50 nM (p<0.001). A 50% inhibitory effect of NaF was obtained at 0.5-1 mM for cytosol and 5 mM for membranes (p<0.001). In Caov-3 cells exposed GnRH, PP2A activity of plasma membrane increased by 1.3-fold (p<0.001) but that of cytosol was not affected. PP2A activity in the plasma membrane of ovarian cancer cells might be distinct from that present in the cytosol. The plasma membrane PP2A may be responsible for a portion of an increased ser/thr protein phosphorylation-dephosphorylation turnover that occurs during cell exposure to GnRH.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:issn
1021-335X
pubmed:author
pubmed:issnType
Print
pubmed:volume
10
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1885-9
pubmed:dateRevised
2007-11-15
pubmed:meshHeading
pubmed-meshheading:14534713-Cell Differentiation, pubmed-meshheading:14534713-Cell Division, pubmed-meshheading:14534713-Cell Line, Tumor, pubmed-meshheading:14534713-Cell Membrane, pubmed-meshheading:14534713-Centrifugation, Density Gradient, pubmed-meshheading:14534713-Cytosol, pubmed-meshheading:14534713-Dose-Response Relationship, Drug, pubmed-meshheading:14534713-Endoplasmic Reticulum, pubmed-meshheading:14534713-Female, pubmed-meshheading:14534713-Gonadotropin-Releasing Hormone, pubmed-meshheading:14534713-Humans, pubmed-meshheading:14534713-Kinetics, pubmed-meshheading:14534713-MAP Kinase Signaling System, pubmed-meshheading:14534713-Okadaic Acid, pubmed-meshheading:14534713-Ovarian Neoplasms, pubmed-meshheading:14534713-Phosphoprotein Phosphatases, pubmed-meshheading:14534713-Phosphorylation, pubmed-meshheading:14534713-Protein Phosphatase 2, pubmed-meshheading:14534713-Signal Transduction, pubmed-meshheading:14534713-Sodium Fluoride, pubmed-meshheading:14534713-Time Factors
pubmed:articleTitle
Independent action of serine/threonine protein phosphatase in ovarian cancer plasma membrane and cytosol during gonadotropin-releasing hormone stimulation.
pubmed:affiliation
Department of Obstetrics and Gynecology, Gifu University School of Medicine, Tsukasamachi, Gifu 500-8705, Japan.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't