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

The different epidermal growth factor (EGF)-related peptides elicit a diverse array of biological responses as the result of their ability to activate distinct subsets of ErbB receptor dimers, leading to the recruitment of different intracellular signaling networks. To specifically examine dimerization-dependent modulation of receptor signaling, we constructed NIH 3T3 cell lines expressing ErbB-1 and ErbB-2 singly and in pairwise combinations with each other ErbB family member. This model system allowed the comparison of EGF-activated ErbB-1 with ErbB-1 activated by Neu differentiation factor (NDF)-induced heterodimerization with ErbB-4. In both cases, ErbB-1 coupled to the adaptor protein Shc, but only when activated by EGF was it able to interact with Grb2. Compared to the rapid internalization of EGF-activated ErbB-1, NDF-activated ErbB-1 showed delayed internalization characteristics. Furthermore, the p85 subunit of phosphatidylinositol kinase (PI3-K) associated with EGF-activated ErbB-1 in a biphasic manner, whereas association with ErbB-1 transactivated by ErbB-4 was monophasic. The signaling properties of ErbB-2 following heterodimerization with the other ErbB receptors or homodimerization induced by point mutation or monoclonal antibody treatment were also analyzed. ErbB-2 binding to peptides containing the Src homology 2 domain of Grb2 or p85 and the phosphotyrosine binding domain of Shc varied according to the mode of receptor activation. Finally, tryptic phosphopeptide mapping of both ErbB-1 and ErbB-2 revealed that receptor phosphorylation is dependent on the dimerization partner. Differential receptor phosphorylation may, therefore, be the basis for the differences in the signaling properties observed.
Mol Cell Biol 1998 Sep
PMID:ErbB-1 and ErbB-2 acquire distinct signaling properties dependent upon their dimerization partner. 971 May 88

The sphingomyelin derivative ceramide is a signaling molecule implicated in numerous physiological events. Recently published reports indicate that ceramide levels are elevated in insulin-responsive tissues of diabetic animals and that agents which trigger ceramide production inhibit insulin signaling. In the present series of studies, the short-chain ceramide analog C2-ceramide inhibited insulin-stimulated glucose transport by approximately 50% in 3T3-L1 adipocytes, with similar reductions in hormone-stimulated translocation of the insulin-responsive glucose transporter (GLUT4) and insulin-responsive aminopeptidase. C2-ceramide also inhibited phosphorylation and activation of Akt, a molecule proposed to mediate multiple insulin-stimulated metabolic events. C2-ceramide, at concentrations which antagonized activation of both glucose uptake and Akt, had no effect on the tyrosine phosphorylation of insulin receptor substrate 1 (IRS-1) or the amounts of p85 protein and phosphatidylinositol kinase activity that immunoprecipitated with anti-IRS-1 or antiphosphotyrosine antibodies. Moreover, C2-ceramide also inhibited stimulation of Akt by platelet-derived growth factor, an event that is IRS-1 independent. C2-ceramide did not inhibit insulin-stimulated phosphorylation of mitogen-activated protein kinase or pp70 S6-kinase, and it actually stimulated phosphorylation of the latter in the absence of insulin. Various pharmacological agents, including the immunosuppressant rapamycin, the protein synthesis inhibitor cycloheximide, and several protein kinase C inhibitors, were without effect on ceramide's inhibition of Akt. These studies demonstrate ceramide's capacity to inhibit activation of Akt and imply that this is a mechanism of antagonism of insulin-dependent physiological events, such as the peripheral activation of glucose transport and the suppression of apoptosis.
Mol Cell Biol 1998 Sep
PMID:Regulation of insulin-stimulated glucose transporter GLUT4 translocation and Akt kinase activity by ceramide. 971 Jun 29

Phosphatidylinositol kinases play a crucial role in signal transduction in many cell types. The 55 kDa isoform of phosphatidylinositol 4-kinases is a key enzyme in the metabolism of phosphoinositides, which work as regulators of cell function itself or as precursors of signal molecules. The experiments with HaCaT cells presented suggest that the phosphatidylinositol 4-kinase activity in this cell line corresponds to the 55 kDa isoform concerning kinetic parameters and specific activity in comparison with the malignant cell line A431. Km (for ATP and phosphatidyl-inositol) and Ki values (for Ca2+ and adenosine) are in good agreement with the parameters described for other cells. The findings support the idea that the 55 kDa phosphatidylinositol 4-kinase represents a key enzyme in the inositide signal transduction pathway.
Int J Mol Med 1998 Jul
PMID:Identification of 55 kDa phosphatidylinositol 4-kinase in HaCaT cells: comparison with the epithelial cell line A431. 985 49

A phosphatidylinositol 4-kinase (Ptdlns 4-kinase, M(r) approximately 95,000) from the membranes of the electric organ of Torpedo californica was purified to apparent homogeneity. The Michaelis constant for ATP (KM = 280 +/- 60 microM at 20 degrees C) and the inhibition constant for adenosine (Ki = 0.4 mM at 20 degrees C) qualify the electrocyte Ptdlns 4-kinase as a type III kinase. The Ptdlns 4-kinase phosphorylates preferentially exogenous Ptdlns, added in the form of mixed Ptdlns/Triton X-100 micelles, whereas endogenously bound Ptdlns in the membrane fragments of electrocytes is a very poor substrate. It is important that the enzyme and the substrate Ptdlns are situated in different lipid bilayers. The catalytic turnover constant for exogenous Ptdlns is k = 55.3 +/- 6 min-1 at 20 degrees C and the molar Triton X-100/Ptdlns ratio of 16:1. For the substrate Ptdlns in the 'micellar solvent' Triton X-100, steady state kinetics were analysed in terms of the mole fraction X = n(Ptdlns)/[n(Ptdlns) + n(Triton X)] yielding the characteristic Michaelis mole fraction XM = 0.019 +/- 0.005 at 20 degrees C. The activity of the enzyme was enhanced about 5-fold in the presence of Triton X-114, yielding k = 277 +/- 30 min-1 at 20 degrees C. Triton X-114 has a shorter head-group, indicating that the vicinity of the Ptdlns head group in the mixed micelles should not be screened by bulky neighbours. The inhibition of the enzyme activity by Ca2+ is highly cooperative yielding the Hill inhibition constant Ki = 0.47 +/- 0.1 mM and the Hill coefficient h = 3.6 +/- 0.5. The enthalpy of activation is 100 +/- 10 kJ/mol between 0 degree C and 20 degrees C. Although the Ptdlns 4-kinase can be affinity-chromatographically copurified with the nicotinic acetylcholine (AcCho) receptor, suggesting tight association between the two proteins. AcCho does not affect the activity of the Ptdlns 4-kinase in the presence of the AcCho receptor.
Mol Membr Biol
PMID:Phosphatidylinositol 4-kinase of Torpedo californica electrocytes: physico-chemical characterization and regulation by calcium and vicinal molecules of phosphatidylinositol. 985 9

One or more free hydroxyls of the phosphatidylinositol (PtdIns) head group undergo enzymatic phosphorylation, yielding phosphoinositides (PIs) with key functions in eukaryotic cellular regulation. Two such species, PtdIns 5-P and PtdIns 3,5-P(2), have now been identified in mammalian cells, but their biosynthesis remains unclear. We have isolated a novel mammalian PI kinase, p235, whose exact substrate specificity remained to be determined (Shisheva, A., Sbrissa, D., and Ikonomov, O. (1999) Mol. Cell. Biol. 19, 623-634). Here we report that recombinant p235 expressed in COS cells, like the authentic p235 in adipocytes, displays striking specificity for PtdIns over PI substrates and generates two products identified as PtdIns 5-P and PtdIns 3,5-P(2) by HPLC analyses. Synthetic PtdIns 3-P substrates were also converted to PtdIns 3,5-P(2) but to a substantially lesser extent than PtdIns isolated from natural sources. Important properties of the p235 PI 5-kinase include high sensitivity to nonionic detergents and relative resistance to wortmannin and adenosine. By analyzing deletion mutants in a heterologous cell system, we determined that in addition to the predicted catalytic domain other regions of the molecule are critical for the p235 enzymatic activity. HPLC resolution of monophosphoinositide products, generated by p235 immune complexes derived from lysates of 3T3-L1 adipocytes acutely stimulated with insulin, revealed essentially the same PtdIns 5-P levels as the corresponding p235 immune complexes of resting cells. However, the acute insulin action resulted in an increase of a wortmannin-sensitive PtdIns 3-P peak, suggestive of a plausible recruitment of wortmannin-sensitive PI 3-kinase(s) to p235. In conclusion, mouse p235 (renamed here PIKfyve) displays a strong in vitro activity for PtdIns 5-P and PtdIns 3,5-P(2) generation, implying PIKfyve has a key role in their biosynthesis.
 ...
PMID:PIKfyve, a mammalian ortholog of yeast Fab1p lipid kinase, synthesizes 5-phosphoinositides. Effect of insulin. 1041 65

DNA damage checkpoints lead to the inhibition of cell cycle progression following DNA damage. The Saccharomyces cerevisiae Mec1 checkpoint protein, a phosphatidylinositol kinase-related protein, is required for transient cell cycle arrest in response to DNA damage or DNA replication defects. We show that mec1 kinase-deficient (mec1kd) mutants are indistinguishable from mec1Delta cells, indicating that the Mec1 conserved kinase domain is required for all known Mec1 functions, including cell viability and proper DNA damage response. Mec1kd variants maintain the ability to physically interact with both Ddc2 and wild-type Mec1 and cause dominant checkpoint defects when overproduced in MEC1 cells, impairing the ability of cells to slow down S phase entry and progression after DNA damage in G(1) or during S phase. Conversely, an excess of Mec1kd in MEC1 cells does not abrogate the G(2)/M checkpoint, suggesting that Mec1 functions required for response to aberrant DNA structures during specific cell cycle stages can be separable. In agreement with this hypothesis, we describe two new hypomorphic mec1 mutants that are completely defective in the G(1)/S and intra-S DNA damage checkpoints but properly delay nuclear division after UV irradiation in G(2). The finding that these mutants, although indistinguishable from mec1Delta cells with respect to the ability to replicate a damaged DNA template, do not lose viability after UV light and methyl methanesulfonate treatment suggests that checkpoint impairments do not necessarily result in hypersensitivity to DNA-damaging agents.
Mol Cell Biol 2001 Jun
PMID:Characterization of mec1 kinase-deficient mutants and of new hypomorphic mec1 alleles impairing subsets of the DNA damage response pathway. 1135 99

Actin assembly on membrane surfaces is an elusive process in which several phosphoinositides (PIPs) have been implicated. We have reconstituted actin assembly using a defined membrane surface, the latex bead phagosome (LBP), and shown that the PI(4,5)P(2)-binding proteins ezrin and/or moesin were essential for this process (). Here, we provide several lines of evidence that both preexisting and newly synthesized PI(4,5)P(2), and probably PI(4)P, are essential for phagosomal actin assembly; only these PIPs were routinely synthesized from ATP during in vitro actin assembly. Treatment of LBP with phospholipase C or with adenosine, an inhibitor of type II PI 4-kinase, as well as preincubation with anti-PI(4)P or anti-PI(4,5)P(2) antibodies all inhibited this process. Incorporation of extra PI(4)P or PI(4,5)P(2) into the LBP membrane led to a fivefold increase in the number of phagosomes that assemble actin. An ezrin mutant mutated in the PI(4,5)P(2)-binding sites was less efficient in binding to LBPs and in reconstituting actin assembly than wild-type ezrin. Our data show that PI 4- and PI 5-kinase, and under some conditions also PI 3-kinase, activities are present on LBPs and can be activated by ATP, even in the absence of GTP or cytosolic components. However, PI 3-kinase activity is not required for actin assembly, because the process was not affected by PI 3-kinase inhibitors. We suggest that the ezrin-dependent actin assembly on the LBP membrane may require active turnover of D4 and D5 PIPs on the organelle membrane.
Mol Biol Cell 2002 Apr
PMID:Phosphoinositides regulate membrane-dependent actin assembly by latex bead phagosomes. 1195 Sep 31

TOR (target of rapamycin) is a phosphatidylinositol kinase-related protein kinase that controls cell growth in response to nutrients. Rapamycin is an immunosuppressive and anticancer drug that acts by inhibiting TOR. The modes of action of TOR and rapamycin are remarkably conserved from S. cerevisiae to humans. The current understanding of TOR and rapamycin is derived largely from studies with S. cerevisiae. In this review, we discuss the contributions made by S. cerevisiae to understanding rapamycin action and TOR function.
Microbiol Mol Biol Rev 2002 Dec
PMID:Elucidating TOR signaling and rapamycin action: lessons from Saccharomyces cerevisiae. 1245 83

Functional assays of genes have historically led to insights about the activities of a protein or protein cascade. However, the rapid expansion of genomic and proteomic information for a variety of diverse taxa is an alternative and powerful means of predicting function by comparing the enzymes and metabolic pathways used by different organisms. As part of the Giardia lamblia genome sequencing project, we routinely survey the complement of predicted proteins and compare those found in this putatively early diverging eukaryote with those of prokaryotes and more recently evolved eukaryotic lineages. Such comparisons reveal the minimal composition of conserved metabolic pathways, suggest which proteins may have been acquired by lateral transfer, and, by their absence, hint at functions lost in the transition from a free-living to a parasitic lifestyle. Here, we describe the use of bioinformatic approaches to investigate the complement and conservation of proteins in Giardia involved in the regulation of translation. We compare an FK506 binding protein homologue and phosphatidylinositol kinase-related kinase present in Giardia to those found in other eukaryotes for which complete genomic sequence data are available. Our investigation of the Giardia genome suggests that PIK-related kinases are of ancient origin and are highly conserved.
Comp Biochem Physiol B Biochem Mol Biol 2002 Dec
PMID:Inferring protein function from genomic sequence: Giardia lamblia expresses a phosphatidylinositol kinase-related kinase similar to yeast and mammalian TOR. 1247 Aug 13

We have identified a novel pathway of ataxia telangiectasia mutated (ATM) and DNA-dependent protein kinase (DNA-PK) signaling that results in nuclear factor kappaB (NF-kappaB) activation and chemoresistance in response to DNA damage. We show that the anthracycline doxorubicin (DOX) and its congener N-benzyladriamycin (AD 288) selectively activate ATM and DNA-PK, respectively. Both ATM and DNA-PK promote sequential activation of the mitogen-activated protein kinase (MAPK)/p90(rsk) signaling cascade in a p53-independent fashion. In turn, p90(rsk) interacts with the IkappaB kinase 2 (IKK-2) catalytic subunit of IKK, thereby inducing NF-kappaB activity and cell survival. Collectively, our findings suggest that distinct members of the phosphatidylinositol kinase family activate a common prosurvival MAPK/IKK/NF-kappaB pathway that opposes the apoptotic response following DNA damage.
Mol Cell Biol 2004 Mar
PMID:ATM and the catalytic subunit of DNA-dependent protein kinase activate NF-kappaB through a common MEK/extracellular signal-regulated kinase/p90(rsk) signaling pathway in response to distinct forms of DNA damage. 1496 65


<< Previous 1 2 3 4 5 6 7 8 Next >>