Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mitogen-activated protein kinase (p42mapk) becomes transiently activated after treatment of serum-starved murine Swiss 3T3 cells or EL4 thymocytes with a diversity of mitogens. Similarly, a meiosis-activated protein kinase (p44mpk) becomes stimulated during maturation of sea star oocytes induced by 1-methyladenine. Both p42mapk and p44mpk have been identified as protein-serine/threonine kinases that are activated as a consequence of their phosphorylation. Because homologous protein kinases may play essential roles in both mitogenesis and oogenesis, we have compared in detail the biochemical properties of these two kinases. We find that these kinases are highly related based on their in vitro substrate specificities, sensitivity to inhibitors, and immunological cross-reactivity. However, they differ in apparent molecular weight and can be separated chromatographically, indicating that the two enzymes are distinct. Furthermore, in the course of this investigation, we have identified a 44-kDa protein kinase in mitogen-stimulated Swiss mouse 3T3 cells and EL4 thymocytes that co-purifies with p44mpk and thus appears to be a closer homolog of the sea star enzyme. Analysis of these protein kinases clarifies the relationships between a set of tyrosine-phosphorylated 41-45-kDa proteins present in mitogen-stimulated cells (Martinez, R., Nakamura., K. D., and Weber, M. J. (1982) Mol. Cell. Biol. 2, 653-655; Cooper, J. A., and Hunter, T. (1984) Mol. Cell. Biol. 4, 30-37), two myelin basic protein kinases identified in epidermal growth factor-treated Swiss mouse 3T3 cells (Ahn, N. G., Weiel, J. E., Chan, C. P., and Krebs, E. G. (1990) J. Biol. Chem. 265, 11487-11494), and p42mapk. Our work points to the existence of a group of related serine/threonine protein kinases, regulated by tyrosine phosphorylation and functioning at different stages of the cell cycle.
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PMID:Biochemical characterization of a family of serine/threonine protein kinases regulated by tyrosine and serine/threonine phosphorylations. 165 19

Cyclic AMP regulates a variety of cellular responses through activation of the catalytic subunit of cAMP-dependent protein kinase. The cDNAs for two protein isoforms of the catalytic subunit, C alpha and C beta, were placed into expression vectors, and their ability to stimulate cAMP-dependent transcription of the human enkephalin promoter was examined in transiently transfected CV-1 cells. Expression vectors for C alpha and C beta that were directed by the human cytomegalovirus promoter produced up to 350- and 200-fold increases in chloramphenicol acetyltransferase activity, respectively, when cotransfected with the ENKAT-12 reporter plasmid. Transcriptional activation was shown to be dependent upon functional kinase activity by point mutations in catalytic subunit vectors which eliminated activation. Transcriptional activation by C alpha and C beta was eliminated when the cAMP response elements (CREs) were deleted from the native enkephalin promoter, but activation was recovered when this region was replaced with an oligonucleotide containing two copies of the somatostatin CRE consensus TGACGTCA. C alpha expression vectors were found to produce 2-fold greater transcriptional activation than C beta expression vectors. These results were most likely due to the cellular kinase activity produced by the catalytic subunit expression vectors and did not appear to be dependent on CRE motif or substrate specificity. In vitro mutagenesis indicates that neither C alpha nor C beta requires N-terminal myristylation for transcriptional activation, but threonine-197 is critical to subunit function.
Mol Endocrinol 1991 Jul
PMID:Regulation of the human enkephalin promoter by two isoforms of the catalytic subunit of cyclic adenosine 3',5'-monophosphate-dependent protein kinase. 165 33

We have investigated the ability of amino acid analogues of serine and threonine to inhibit the increase in steroidogenesis elicited by addition of ACTH or cAMP in cells isolated from the rat adrenal cortex. We have found that the serine analogues, D, L-isoserine, alpha-methyl-D, L-serine and L-homoserine, are almost totally ineffective in inhibiting this process but that the threonine analogue, D, L-beta-hydroxynorvaline, at a concentration of 300 microM inhibits stimulated steroid hormone biosynthesis by ca 95%, while inhibiting overall protein synthesis by only ca 40%. This inhibition was found to occur in a dose-dependent manner and to be reversible by a stoichiometric concentration of threonine. These studies suggest that beta-hydroxynorvaline is functioning as a threonine analogue in our experimental system. Both the onset of inhibition by analogue and reversal of this inhibition by the natural amino acid occurred rapidly, without detectable lag. Since results obtained using cAMP as stimulant parallel those obtained using ACTH, the inhibitory effect of the analogue seems to occur subsequent to the synthesis of cAMP. Additionally, the analogue does not inhibit the conversion of pregnenolone to corticosterone, suggesting the site of action of analogue occurs prior to the synthesis of pregnenolone from cholesterol. Thus, the analogue may be exerting its effect on a protein that is synthesized subsequent to ACTH addition and is important in the acute phase of stimulated steroid hormone biosynthesis. Further, since ACTH action on adrenal cortex cells causes the activation of protein kinase A, which phosphorylates serine and threonine residues, it is possible that the effect of the analogue is to prevent the phosphorylation of a newly-synthesized protein.
J Steroid Biochem Mol Biol 1991
PMID:Inhibition of steroidogenesis in rat adrenal cortex cells by a threonine analogue. 165 80

We have used okadaic acid (OA), a cell-permeable inhibitor of serine/threonine protein phosphatase types 1 (PP-1) and 2A (PP-2A), to demonstrate that the subcellular distribution of glucocorticoid receptor (GR) in rat fibroblasts is influenced by its phosphorylation state. Nuclear GRs in OA-treated cells retain transcriptional enhancement activity. Nuclear import or export of hormone agonist-bound GRs is not affected by OA. However, a dose of OA that fully inhibits PP-2A and partially inhibits PP-1, but not a lower dose that only partially inhibits PP-2A, leads to inefficient nuclear retention of agonist-bound GRs, and their redistribution into the cytoplasm. These receptors appear to be trapped in the cytoplasmic compartment and are unable to recycle (i.e. reenter the nucleus). Addition of OA during different steps of GR recycling demonstrates that OA must be present during nuclear export of GRs to block GR recycling. A direct role for PP-1 and/or PP-2A in GR recycling is suggested by site-specific hyperphosphorylation of GRs in vivo during OA inhibition of recycling. These are the same sites that undergo in vitro site-specific dephosphorylation by PP-1 and PP-2A. The block in GR recycling that results from inhibition of PP-1 and/or PP-2A resembles effects previously observed in v-mos-transformed rat fibroblasts. Interestingly, OA inhibition of PP-2A in v-mos-transformed cells leads to the reversal of oncoprotein effects on GR recycling and retention of receptors within the nuclear compartment. We propose that GR recycling is influenced by the activities of distinct protein phosphatases (PP-1 and/or PP-2A), and that the interference of this pathway observed in v-mos-transformed cells may be the result of effects of the oncoprotein on the phosphatases or a specific subset of their targets.
Mol Endocrinol 1991 Sep
PMID:Protein phosphatase types 1 and/or 2A regulate nucleocytoplasmic shuttling of glucocorticoid receptors. 166 12

A unique feature of neuronal calcium/calmodulin-stimulated protein kinase II (CaM-PK II) is its autophosphorylation. A number of sites are involved and, depending on the in vitro conditions used, three serine and six threonine residues have been tentatively identified as autophosphorylation sites in the alpha subunit. These sites fall into three categories. Primary sites are phosphorylated in the presence of calcium and calmodulin, but under limiting conditions of temperature, ATP, Mg2+, or time. Secondary sites are phosphorylated in the presence of calcium and calmodulin under nonlimiting conditions. Autonomous sites are phosphorylated in the absence of calcium and calmodulin after initial phosphorylation of Thr-286. Mechanisms that lead to a decrease in CaM-PK II autophosphorylation include the thermolability of the enzyme and the activity of protein phosphatases. A range of in vitro inhibitors of CaM-PK II autophosphorylation have recently been identified. Autophosphorylation of CaM-PK II leads to a number of consequences in vitro, including generation of autonomous activity and subcellular redistribution, as well as alterations in conformation, activity, calmodulin binding, substrate specificity, and susceptibility to proteolysis. It is established that CaM-PK II is autophos-phorylated in neuronal cells under basal conditions. Depolarization and/or activation of receptors that lead to an increase in intracellular calcium induces a marked rise in the autophosphorylation of CaM-PK II in situ. The incorporation of phosphate is mainly found on Thr-286, but other sites are also phosphorylated at a slower rate. One consequence of the increase in CaM-PK II autophosphorylation in situ is an increase in the level of autonomous kinase activity. It is proposed that the formation of an autonomous enzyme is only one of the consequences of CaM-PK II autophosphorylation in situ and that some of the other consequences observed in vitro will also be seen. CaM-PK II is involved in the control of neuronal plasticity, including neurotransmitter release and long-term modulation of postreceptor events. In order to understand the function of CaM-PK II, it will be essential to ascertain more fully the mechanisms of its autophosphorylation in situ, including especially the sites involved, the consequences of this autophosphorylation for the kinase activity, and the relationships between the state of CaM-PK II autophosphorylation and the physiological events within neurons.
Mol Neurobiol 1991
PMID:Autophosphorylation of neuronal calcium/calmodulin-stimulated protein kinase II. 166 85

Data emerging from a number of different systems indicate that protein phosphatases are highly regulated and potentially responsive to changes in the levels of intracellular second messengers produced by extracellular stimulation. They may therefore be involved in the regulation of many cell functions. The protein phosphatases in the nervous system have not been well studied. However, a number of neuronal-specific regulators (such as DARPP-32 and G-substrate) exist, and brain protein phosphatases appear to have particularly low specific activity, suggesting that neuronal protein phosphatases possess considerable and unique potential for regulation. Several early events following depolarization or receptor activation appear to involve specific dephosphorylations, indicating that regulation of protein phosphatase activity is important for the control of many neuronal functions. This article reviews the current literature concerning the identification, regulation, and function of serine/threonine protein phosphatases in the brain, with particular emphasis on the regulation of the major protein phosphatases, PP1 and PP2A, and their potential roles in modulating neurotransmitter release and postsynaptic responses.
Mol Neurobiol 1991
PMID:The regulation and function of protein phosphatases in the brain. 166 87

Neuronal cells are known to express at least two different forms of the C-SRC proto-oncogene as a consequence of alternative splicing events which add an 18-nucleotide exon (the NI exon) between C-SRC exons 3 and 4. Here we report that a second neuronal exon of C-SRC is also present between C-SRC exons 3 and 4. This neuronal exon (the NII exon) of C-SRC was isolated from human adult and fetal brain-derived cDNAs and contains 33 nucleotides capable of encoding 11 amino acids (Gln-Thr-Trp-Phe-Thr-Phe-Arg-Trp-Leu-Gln-Arg). The human NI exon was located approximately 390 nucleotides from the end of C-SRC exon 3, whereas the NII exon was approximately 1,000 nucleotides from the beginning of C-SRC exon 4. Analysis of human brain RNA revealed that the NII exon is utilized primarily in conjunction with the NI exon to yield transcripts capable of encoding C-SRC products possessing 17 additional amino acids. These splicing events, which occur between the NI and NII exons, are predicted to alter the sixth amino acid encoded by the NI exon from an arginine to a serine residue, producing a potentially novel phosphorylation site. Analysis of the different C-SRC RNA transcripts revealed that the level of C-SRC RNA containing both NI and NII exons is similar in adult and fetal brain tissue, whereas the level of C-SRC RNA containing only the NI exon or the nonneuronal form of C-SRC RNAs is significantly higher in fetal brain tissues. These results indicate that the expression and splicing pattern of the C-SRC gene are developmentally regulated in the human brain.
Mol Cell Biol 1990 May
PMID:Identification of a novel neuronal C-SRC exon expressed in human brain. 169 39

The product of the HER-2 proto-oncogene, p185HER-2, was found to be amplified approximately 10-fold in the human breast carcinoma cell line, BT474, compared to a cell line, HBL-100, derived from normal breast tissue. To explore the possible role of p185HER-2 in growth of the breast carcinoma cells, we investigated factors that may modulate cell growth and phosphorylation of the HER-2 protein product. Two growth factors, epidermal growth factor (EGF) and insulin, stimulated phosphorylation of the HER-2 protein product. In response to insulin, the phosphoserine and phosphothreonine content in p185HER-2 was transiently enhanced about 6-fold. When EGF was added to BT474 cells there was 2- to 3-fold enhanced phosphorylation of serine and threonine residues in p185HER-2 which was maintained for at least 60 min. Although p185HER-2 has been found to be phosphorylated on tyrosine residues following EGF treatment of several different cell types, we estimate that less than 1% of the protein contained phosphotyrosine in the BT474 cells.
Mol Cell Endocrinol 1990 Mar 05
PMID:Insulin and epidermal growth factor stimulate phosphorylation of p185HER-2 in the breast carcinoma cell line, BT474. 169 19

From a Plasmodium falciparum cDNA expression library derived from mRNA of the asexual blood stages, we isolated and sequenced five different cDNA clones whose predicted protein products were unusually rich in asparagine (Asn). Two of the clones, R5 and G5, contain tandem imperfectly repeated sequences based on Asn-Asn-Thr (NNT) and Asn-Asn-Met (NNM) respectively. The other three, E4, C5 and R13, as well as G5, contain stretches of polyasparagine varying in length from 2 to 26 residues. Results of DNA blotting experiments with the individual cDNA sequences as probes suggest that each of the five clones corresponds to a different P. falciparum gene. The fragments of P. falciparum proteins expressed by the cDNA clones shared cross-reactive antigenic determinants which were present on multiple P. falciparum proteins. In immunoblotting experiments, owl monkey antibodies selected for binding to the polypeptide expressed by clone E4, C5 or G5 reacted with the expressed proteins from all 5 clones, and with at least 10 proteins from schizont infected erythrocytes. The cross-reactive epitopes could be modeled by two Asn-rich peptide structures: (1) (NNT)8, whose sequence was based on the R5 repeat; and (2) (NPNA)6, whose sequence was based on the Asn-rich repeat of the P. falciparum circumsporozoite protein (CSP). Antibodies that bound to each peptide were selected from sera of immune monkeys that had never been exposed to sporozoites. The selected antibodies bound all 5 expressed proteins in immunoblotting assays and also bound to several proteins from parasitized erythrocytes. Such cross reactivity between the CSP repeating unit and several blood-stage antigens has not been previously reported.
Mol Biochem Parasitol 1990 Apr
PMID:Cross-reactive asparagine-rich determinants shared between several blood-stage antigens of Plasmodium falciparum and the circumsporozoite protein. 169 14

The equilibrium and kinetic behavior of the guanidine hydrochloride (Gdn-HCl) induced unfolding/refolding of four bovine pancreatic trypsin inhibitor (BPTI) mutants was examined by using ultraviolet difference spectroscopy. In three of the mutants, we replaced the buried 30-51 disulfide bond with alanine at position 51 and valine (Val30/Ala51), alanine (Ala30/Ala51), or threonine (Thr30/Ala51) at position 30. For the fourth mutant, the solvent-exposed 14-38 disulfide was substituted by a pair of alanines (Ala14/Ala38). All mutants retained the 5-55 disulfide. Experiments were performed under oxidizing conditions; thus, both the unfolded and folded forms retained two native disulfide bonds. Equilibrium experiments demonstrated that all four mutants were destabilized relative to wild-type BPTI. However, the stability of the 30-51 mutants increased with the hydrophobicity of the residue substituted at position 30. Kinetic experiments showed that all four mutants contained two minor slow refolding phases with characteristics of proline isomerization. The specific behavior of the phases depended on the location of the disulfide bonds. The major unfolding/refolding phase for each of the 30-51 mutants was more than an order of magnitude slower than for Ala14/Ala38 or for BPTI in which the 14-38 disulfide bond was specifically reduced and blocked with iodoacetamide [Jullien, M., & Baldwin, R. L. (1981) J. Mol. Biol. 145, 265-280]. Since this effect is independent of the stability of the protein, it is consistent with a model in which the proper docking of the interior residues of the protein is the rate-limiting step in the folding of these mutants.
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PMID:Denaturant-dependent folding of bovine pancreatic trypsin inhibitor mutants with two intact disulfide bonds. 169 24


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