Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P67775 (alpha isoform)
 797 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Purification of type 2A protein phosphatase (PP2A) from rabbit skeletal muscle resulted in the isolation of a trimeric phosphatase which is composed of a catalytic (PP2Ac), a structural (PR65alpha/Aalpha), and a regulatory (PR55alpha/Balpha) subunit, together with translation termination factor 1 (eRF1) and another protein of 55 kD (EMBO J., 15, 101-112). Yeast two-hybrid system analysis demonstrated that the eRF1 interacted with PP2Acalpha but not with PR65alpha/Aalpha or PR55alpha/Balpha. The N-terminal region of PP2Acalpha, comprising 50 amino acid residues, and the C-terminal part of eRF1, corresponding to an internal region between amino acids 338-381, were found to be necessary for eRF1--PP2Acalpha interaction in yeast. Immunoprecipitations using 12CA5 antibodies and extracts from COS1 cells transiently transfected with eRF1 tagged with 9-amino acid epitope from influenza hemagglutinin (HA) demonstrated the presence of eRF1--PP2Acalpha--PR65alpha/Aalpha complex in these cells. In addition, polysomes obtained from COS1 cells overexpressing HA--eRF1 displayed several-fold higher PP2A activity than control polysomes. No effect of either PP2Ac or dimeric and trimeric PP2A holoenzymes on the rate of translation termination was detected using an in vitro reconstituted translation termination assay. In summary, eRF1 appears to represent a novel PP2A-targeting subunit that brings this phosphatase in contact with putative ribosomal substrate(s). It remains to be established whether termination of translation requires dephosphorylation of participating protein factor(s).
Biochemistry (Mosc) 1999 Dec
PMID:Eukaryotic translation termination factor 1 associates with protein phosphatase 2A and targets it to ribosomes. 1064 61

Phosphorylation by cAMP-dependent protein kinase (PKA) regulates a vast number of cellular functions. An important target for PKA in brain and heart is the class C L-type Ca(2+) channel (Ca(v)1.2). PKA phosphorylates serine 1928 in the central, pore-forming alpha(1C) subunit of this channel. Regulation of channel activity by PKA requires a proper balance between phosphorylation and dephosphorylation. For fast and specific signaling, PKA is recruited to this channel by an protein kinase A anchor protein (Davare, M. A., Dong, F., Rubin, C. S., and Hell, J. W. (1999) J. Biol. Chem. 274, 30280-30287). A phosphatase may be associated with the channel to effectively balance serine 1928 phosphorylation by channel-bound PKA. Dephosphorylation of this site is mediated by a serine/threonine phosphatase that is inhibited by okadaic acid and microcystin. We show that immunoprecipitation of the channel complex from rat brain results in coprecipitation of PP2A. Stoichiometric analysis indicates that about 80% of the channel complexes contain PP2A. PP2A directly and stably binds to the C-terminal 557 amino acids of alpha(1C). This interaction does not depend on serine 1928 phosphorylation and is not altered by PP2A catalytic site inhibitors. These results indicate that the PP2A-alpha(1C) interaction constitutively recruits PP2A to the channel complex rather than being a transient substrate-catalytic site interaction. Functional assays with the immunoisolated class C channel complex showed that channel-associated PP2A effectively reverses serine 1928 phosphorylation by endogenous PKA. Our findings demonstrate that both PKA and PP2A are integral components of the class C L-type Ca(2+) channel that determine the phosphorylation level of serine 1928 and thereby channel activity.
J Biol Chem 2000 Dec 15
PMID:Protein phosphatase 2A is associated with class C L-type calcium channels (Cav1.2) and antagonizes channel phosphorylation by cAMP-dependent protein kinase. 1098 83

CTP:phosphocholine cytidylyltransferase (CCT) is a rate-determining enzyme in de novo synthesis of phosphatidylcholine (PC). The lung requires a steady synthesis of PC for lung surfactant of which disaturated PC is the essential active agent. Surfactant synthesis occurs in alveolar type II cells. Studies with non-pulmonary cells have suggested that CCT is both a nuclear and cytoplasmic protein. The unusual requirements of the lung for PC synthesis and, therefore, CCT activity suggest a unique mechanism of regulation and possibly localization of CCT. The localization of CCT alpha in lung epithelial cells and, of greater consequence, lung tissues are yet unknown. Three isoforms of CCT have been identified. Herein we investigated the localization of the ubiquitously expressed CCT alpha isoform. To ascertain CCT alpha localization in lungs and lung-related epithelial cells, we employed a number of localization methods. Immunogold electron microscopy using polyclonal antibodies raised to either the carboxyl terminus, catalytic domain, or amino terminus of CCT alpha localized CCT alpha mostly to the exterior plasma membrane or regions of the endoplasmic reticulum (ER) in both A549 and MLE-15 epithelial lung cell lines and primary cultures of fetal rat lung epithelial cells. In contrast to other studies, little or no nuclear labeling was observed. Indirect immunofluorescence of these cells with anti-CCT alpha antibodies resulted in a similar distribution. Indirect visualization of both hemagglutinin- and FLAG-tagged CCT alpha as well as direct visualization of enhanced green fluorescence protein-CCT alpha fusion protein corroborated a cytoplasmic localization of CCT alpha in pulmonary cells. Moreover, analysis of lung tissue from fetal and adult mouse by either immunogold electron microscopy or indirect immunofluorescence yielded a strong cytoplasmic CCT alpha signal with virtually no nuclear localization in epithelial cells lining the airways. The cytoplasmic localization of CCT alpha in type II cells was further substantiated with transgenic mice overexpressing FLAG-tagged CCT alpha using the lung-specific human surfactant protein C (SP-C) promoter. We conclude that CCT alpha does not localize to the nucleus in pulmonary tissues, and, therefore, nuclear localization of CCT alpha is not a universal event.
J Biol Chem 2001 Dec 28
PMID:CTP:phosphocholine cytidylyltransferase alpha is a cytosolic protein in pulmonary epithelial cells and tissues. 1158 89

Nuclear factor-kappa B (NF-kappa B)/Rel transcription factors are key regulators of a variety of genes involved in inflammatory responses, growth, differentiation, apoptosis, and development. There are increasing lines of evidence that NF-kappa B/Rel activity is controlled to a great extent by its phosphorylation state. In this study, we demonstrated that RelA physically associated with protein phosphatase 2A (PP2A) subunit A (PR65). Both the N- and C-terminal regions of RelA were responsible for the PP2A binding. RelA co-immunoprecipitated with PP2A in melanocytes in the absence of stimulation, indicating that RelA forms a signaling complex with PP2A in the cells. RelA was dephosphorylated by a purified PP2A core enzyme, a heterodimer formed by the catalytic subunit of PP2A (PP2Ac) and PR65, in a concentration-dependent manner. Okadaic acid, an inhibitor of PP2A at lower concentration, increased the basal phosphorylation of RelA in melanocytes and blocked the dephosphorylation of RelA after interleukin-1 stimulation. Interestingly, PP2A immunoprecipitated from melanocytes was able to dephosphorylate RelA, whereas PP2A immunoprecipitated from melanoma cell lines exhibited decreased capacity to dephosphorylate RelA in vitro. Moreover, in melanoma cells in which I kappa B kinase activity was inhibited by sulindac to a similar level as in melanocytes, the phosphorylation state of RelA and the relative NF-kappa B activity were still higher than those in normal melanocytes. These data suggest that the constitutive activation of RelA in melanoma cells (Yang, J., and Richmond, A. (2001) Cancer Res. 61, 4901-4909) could be due, at least in part, to the deficiency of PP2A, which exhibits decreased dephosphorylation of NF-kappa B/RelA.
J Biol Chem 2001 Dec 21
PMID:Protein phosphatase 2A interacts with and directly dephosphorylates RelA. 1159 5

Neuronal Ca(2+)/calmodulin-dependent protein kinase II (CaM kinase II) plays important roles in the control of nerve functions in response to intracellular Ca(2+) (for reviews [Annu. Rev. Physiol. 57 (1995) 417-445; Trends Neurosci. 17 (1994) 406-412]). Brief Ca(2+) signals activate CaM kinase II, and stimulate an autophosphorylation of Thr-286 which allows the kinase to maintain its activated state even after the Ca(2+) concentration has returned to basal levels [J. Biol. Chem. 264 (1989) 16759-16763; Neuron 3 (1989) 59-70; J. Biochem. 109 (1991) 137-143]. Autophosphorylation of CaM kinase II occurs in situ, but it occurs relatively quickly, within just a few minutes [Endocrinology 134 (1994) 2245-2250; J. Biol. Chem. 268 (1993) 7863-7867; J. Biol. Chem. 265 (1990) 18055-18058]. In the present study, we investigated the involvement of the autophosphorylated/Ca(2+)-independent form of CaM kinase II in neurite outgrowth. When neuroblastoma Neruo2a (Nb2a) cells expressing the alpha isoform of CaM kinase II (Nb2a/alpha cells) were stimulated by plating, they formed neurites. The autophosphorylation of Thr-286 and appearance of Ca(2+)-independent activity preceded the neurite formation. The effect of mutating of the kinase autophosphorylation site replacing Thr-286 with Ala (alpha T286A kinase) or Asp (alpha T286D kinase) was examined. alpha T286A kinase was not converted to a Ca(2+)-independent form, and alpha T286D kinase had Ca(2+)-independent activity significantly as an autophosphorylated kinase. Cells expressing alpha T286D kinase had much longer neurites than Nb2a/alpha cells, whereas cells with alpha T286A kinase did not form neurites. These results indicated that the Ca(2+)-independent form of CaM kinase II autophosphorylated at Thr-286 is involved in neurite outgrowth.
Brain Res Brain Res Protoc 2001 Dec
PMID:Investigation of the Ca(2+)-independent form of Ca(2+)/calmodulin-dependent protein kinase II in neurite outgrowth. 1173 91

Intermediate filament (IF) proteins are constituents of the cytoskeleton, conferring resistance to mechanical stress, and are encoded by a dispersed multigene family. In man we have identified two isoforms (180 and 150 kDa) of the IF protein synemin. Synemin alpha and beta have a very short N-terminal domain of 10 amino acids and a long C-terminal domain consisting of 1243 amino acids for the alpha isoform and 931 amino acids for the beta isoform. An intronic sequence of the synemin beta isoform is used as a coding sequence for synemin alpha. Both mRNA isoforms (6.5 and 7.5 kb) result from alternative splicing of the same gene, which has been assigned to human chromosome 15q26.3. Analyses by Northern and Western blot revealed that isoform beta is the predominant isoform in striated muscles, whereas both isoforms (alpha and beta) are present in almost equal quantities in smooth muscles. Co-transfection and immunolabeling experiments indicate that both synemin isoforms are incorporated with desmin to form heteropolymeric IFs. Furthermore synemin and desmin are found aggregated together in certain pathological situations.
Eur J Biochem 2001 Dec
PMID:Human synemin gene generates splice variants encoding two distinct intermediate filament proteins. 1173 98

The synthesis of mammalian steroid hormones by plants has been reported. However, their physiological role in plants is controversial. The existence of receptor molecules as those of animal cells could provide clues into a possible steroid mechanism of action. Solanum glaucophyllum callus cultures were found to contain not only 17beta-estradiol and estrone but also abundant estrogen binding sites. These sites were specific for 17beta-estradiol ( approximately 550 fmol/mg protein) and could also be competed by the known estrogen receptor (ER) agonist diethylstilbestrol. Antibodies directed against specific sequences of the classical ER alpha isoform, labelled a approximately 67 kDa band which comigrated with the mammalian ER alpha antigen. ER alpha-like proteins were tested positive as estrogen binders in Ligand blot experiments using 17beta-estradiol macromolecular derivatives as ligands. Our results provide first evidences on the existence of estrogen binding proteins structurally related to the mammalian ER alpha subtype in a higher plant system.
Biochem Biophys Res Commun 2001 Dec 21
PMID:Presence of estrogens and estrogen receptor-like proteins in Solanum glaucophyllum. 1174 16

While the role of the class IA phosphoinositide 3-kinase (PI 3-kinase) in insulin signaling is well established, little is known about the role of the class II PI 3-kinases. We show that insulin stimulation of intact rat soleus and epitrochlearis muscles causes a 3- to 4-fold increase in the activity of the wortmannin-resistant alpha isoform of the class II PI 3-kinase (PI3K-C2alpha). This activation is rapid and parallels the insulin-induced activation of the class IA PI 3-kinase associated with IRS-1 in these muscles. However, while contraction activated p38 Map kinase, it did not stimulate the activity of the class II PI 3-kinase. Therefore, activation of class II PI 3-kinase is unlikely to provide a mechanism that explains the fact that exercise-induced activation of glucose uptake is not blocked by wortmannin. However, the results suggest that activation of class II PI 3-kinase is likely to play a role in insulin signaling pathways in skeletal muscle.
Arch Biochem Biophys 2001 Dec 15
PMID:Class II phosphoinositide 3-kinase is activated by insulin but not by contraction in skeletal muscle. 1174 3

Syndecan-4 is a transmembrane heparan sulfate proteoglycan that can regulate cell-matrix interactions and is enriched in focal adhesions. Its cytoplasmic domain contains a central region unlike that of any other vertebrate or invertebrate syndecan core protein with a cationic motif that binds inositol phospholipids. In turn, lipid binding stabilizes the syndecan in oligomeric form, with subsequent binding and activation of protein kinase C. The specificity of phospholipid binding and its potential regulation are investigated here. Highest affinity of the syndecan-4 cytoplasmic domain was seen with phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5P)(2)) and phosphatidylinositol 4-phosphate, and both promoted syndecan-4 oligomerization. Affinity was much reduced for 3-phosphorylated inositides while no binding of diacylglycerol was detected. Syndecan-2 cytoplasmic domain had negligible affinity for any lipid examined. Inositol hexakisphosphate, but not inositol tetrakisphosphate, also had high affinity for the syndecan-4 cytoplasmic domain and could compete effectively with PtdIns(4,5)P(2). Since inositol hexaphosphate binding to syndecan-4 does not promote oligomer formation, it is a potential down-regulator of syndecan-4 signaling. Similarly, phosphorylation of serine 183 in syndecan-4 cytoplasmic domain reduced PtdIns(4,5)P(2) binding affinity by over 100-fold, although interaction could still be detected by nuclear magnetic resonance spectroscopy. Only protein kinase Calpha was up-regulated in activity by the combination of syndecan-4 and PtdIns(4,5)P(2), with all other isoforms tested showing minimal response. This is consistent with the codistribution of syndecan-4 with the alpha isoform of protein kinase C in focal adhesions.
J Biol Chem 2002 Dec 20
PMID:Regulation of inositol phospholipid binding and signaling through syndecan-4. 1237 72

The tachykinins substance P, neurokinin A and neurokinin B are implicated in different diseases and play an important role in neuroimmunomodulation. These peptides interact with three distinct types of tachykinin receptors termed NK(1), NK(2) and NK(3). While most mammalian genes encoding G protein-coupling cell membrane receptors are intron-less, the three tachykinin receptors contain introns in their genomic structures. In the present study, we have identified a splice variant of the tachykinin NK(2) receptor that results from skipping of exon 2 in the processing of the tachykinin NK(2) receptor mRNA. By using reverse transcription-polymerase chain reaction analysis, we observed that the tachykinin NK(2) receptor splice variant, that we named NK(2)beta, appeared in different human and rat tissues that also express the wild type, tachykinin NK(2)alpha isoform. Compared to tachykinin receptor NK(2)alpha isoform mRNA levels, the NK(2)beta isoform was strongly expressed in human and rat uteri, expressed in a moderate degree in the rat urinary bladder, colon, duodenum and stomach and unexpressed in the rat cerebral cortex, kidney, thoracic aorta, skeletal muscle and heart. These data describe the first known tachykinin receptor splice variant and suggest that the variety of tachykinin receptors may be further expanded through the generation of splicing isoforms. The presence of the truncated isoform may have a physiological significance in the regulation of tachykinin NK(2) receptor protein levels.
Life Sci 2002 Dec 06
PMID:Identification of a tachykinin NK(2) receptor splice variant and its expression in human and rat tissues. 1242 86


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