Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0004135 (ATM)
 13,001 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This study demonstrated the existence of a specific binding site for angiotensin IV in porcine aortic endothelial cells. Non-equilibrium kinetic analyses at 37 degrees C allowed the calculation of a kinetic Kd of 0.44 nM. Pseudo-equilibrium saturation binding studies at 37 degrees C for 90 min indicated the presence of a single high-affinity site (Kd = 3.87 +/- 0.60 nM), saturable and abundant (Bmax = 9.64 +/- 1.44 pmol/mg protein). Competitive binding studies demonstrated the following rank order of effectiveness: angiotensin IV > angiotensin III > angiotensin II > angiotensin I > angiotensin II-(1-7), while 2-n-butyl-4-chloro-5-hydroxymethyl-1 [(2'-(1H-tetrazol-5-yl) biphenyl-4-yl) methyl] imidazol (DuP 753: losartan), 1-(4-amino-3-methyl-phenyl) methyl-5-diphenylisoethyl-4,5,6,7-tetrahydro-1H-imidazo [4,5-C] pyridine-6-carboxylic acid (PD 123177) or nicotinic acid-Tyr-(N alpha -benzyl-oxycarbonyl-Arg) Lys-His-Pro-Ile-OH (CGP 42112A) were inactive at the concentration of 100 microM. This binding site is, therefore, distinct from angiotensin II receptors, AT1 and AT2. Addition of the divalent cations Mg2+, Mn2+ or Ca2+ to the incubation buffer resulted in 90-95% inhibition of the [125I]angiotensin IV-specific binding to porcine aortic endothelial cells. Furthermore, the chelator, EGTA, at 5 mM increased the number of binding sites (Bmax = 17.8 +/- 2.5 pmol/mg protein), with no change in affinity (Kd = 5.7 +/- 1.3 nM). Exposure of porcine aortic endothelial cell membranes to the non-hydrolyzable GTP analog, GTP gamma S, had no effect on [125I]angiotensin IV binding. The presence of a high concentration of binding sites for angiotensin IV in porcine aortic endothelial cells suggests that this peptide may play an important role in the modulation of the cardiovascular system.
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PMID:Pharmacological characterization of a specific binding site for angiotensin IV in cultured porcine aortic endothelial cells. 881 53

The coupling of agonist-activated seven transmembrane domain receptors to G proteins is known to involve the amino-terminal region of their third cytoplasmic loop. Analysis of the amino acids in this region of the rat type in angiotensin (AT1a) receptor identified Leu-222 as an essential residue in receptor activation by the physiological agonist, angiotensin II (Ang II). Nonpolar replacements for Leu-222 yielded functionally intact AT1 receptors, while polar or charged residues caused progressive impairment of Ang II-induced inositol phosphate generation. The decrease in agonist-induced signal generation was associated with a parallel reduction of receptor internalization, and was most pronounced for the Lys-222 mutant receptor. Although this mutant showed normal binding of the peptide antagonist, [Sar1,Ile6]Ang II, its affinity for Ang II was markedly reduced, consistent with its inability to adopt the high-affinity conformation. A search revealed that many Gq-coupled receptors contain an apolar amino acid (frequently leucine) in the position corresponding to Leu-222 of the AT1 receptor. These findings suggest that such a conserved apolar residue in the third intracellular loop is a crucial element in the agonist-induced activation of the AT1 and possibly many other G protein-coupled receptors.
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PMID:Dependence of agonist activation on a conserved apolar residue in the third intracellular loop of the AT1 angiotensin receptor. 881 47

1. Several residues critically involved in AT1 receptor ligand-binding and activation have now been identified based on mutational and biochemical studies. 2. Asp281 and Lys199 of the rat AT1 receptor ion-pair with Arg2 and the Phe3 alpha-COOH of angiotensin II (AngII), respectively, and the Asp281/Arg2 interaction is critical for full agonist activity. 3. Agonist activity of AngII also requires an interaction of the Phe8 side chain with His256, which is achieved by docking of the alpha-COOH with Lys199. Non-peptide agonists interact with Lys199 and His256 in a similar fashion. 4. The crucial acid pharmacophores of AngII and the non-peptide antagonist, losartan, appear to occupy the same space within the receptor pocket. Binding of the tetrazole anion moiety of losartan involves multiple contacts, such as Lys199 and His256. However, this interaction does not involve a conventional salt bridge, but rather an unusual lysine-aromatic interaction. 5. Asp1 of AngII forms an ion-pair with His183, which stabilizes the receptor-bound conformation of AngII but is not critical for receptor activation. 6. These interactions and the involvement of other residues in stabilizing the wild-type receptor conformation or in receptor/G-protein coupling are considered here. 7. Despite these insights, considerable effort is still needed to elucidate how ligand binding induces receptor activation, what determines the specificity of AT1 receptor coupling to multiple G-proteins and the in vivo role of receptor down-regulation.
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PMID:Molecular determinants of peptide and non-peptide binding to the AT1 receptor. 899 41

A fifth transmembrane domain lysine residue is conserved in both the type 1 (AT1) and type 2 (AT2) angiotensin II (AngII) receptors. This lysine (Lys199) is believed to play a critical role in peptide binding for the AT1 receptor. To evaluate its possible role in the AT2 receptor, the analogous AT2 residue (Lys199) was changed to glutamine. This mutation greatly reduced the affinity for both 125I-AngII and 125I-Sar1,Ile8-AngII and abolished binding to the non-peptide 125I-PD122979. These data indicate that despite a relatively low homology of 34%, some commonalities in the binding mechanism for AngII may exist between the two subtypes.
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PMID:Mutation of a conserved fifth transmembrane domain lysine residue (Lys215) attenuates ligand binding in the angiotensin II type 2 receptor. 942 26

Studies on ligand-receptor interaction of Angiotensin II (Ang II) receptor type 1 have shown that for peptidic ligands to bind this receptor they must interact via their C-terminal carboxylate group to the positively charged side chain of the Lysine residue 199 located in the fifth transmembrane domain of this receptor. In the Ang II receptor type AT2, this Lysine residue is conserved at position 215 in the fifth transmembrane domain. To determine the specific mechanism of ligand binding to the Angiotensin II receptor type AT2, mutated AT2 receptors were generated in which the Lys215 was replaced with glutamic acid, glutamine, alanine and arginine. The ability of these mutated receptors to bind peptidic ligands 125I-[Sar1-Ile8]Ang II (non-specific for AT2 receptor type), 125I-CGP42112A (AT2 receptor specific) and the non-peptidic ligand PD123319 (AT2 receptor specific) was evaluated by expressing these receptors in Xenopus oocytes and performing binding assays. The Lys215Glu and Lys215Gln mutants of AT2 receptor lost their affinity to 125I-[Sar1-Ile8]Ang II, but retained their affinity to 125I-CGP42112A and PD123319. In contrast, Lys215Arg mutant retained its affinity to 125I-[Sar1-Ile8]Ang II, but exhibited lower affinity to 125I-CGP42112A. The Lys215Ala mutant lost its affinity to both 125I-[Sar1-Ile8]Ang II and 125I-CGP42112A. These results suggest that the binding mechanism of 125I-[Sar1-Ile8]Ang II to AT2 receptor is similar to that of AT1 receptor since an amino acid with positively charged side chain (Lys or Arg) located in the fifth transmembrane domain is required for this ligand to bind AT2 receptor. In contrast, although CGP42112A is a peptidic ligand, it does not require an interaction between its C-terminal carboxylate group and the positively charged side-chain of an amino acid in the fifth transmembrane domain for its binding to AT2 receptor.
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PMID:Role of Lys215 located in the fifth transmembrane domain of the AT2 receptor in ligand-receptor interaction. 953 73

The predominant angiotensin II receptor expressed in the human myometrium is the angiotensin AT2 receptor. This preparation was used for a structure-activity relationship study on angiotensin II analogues modified in positions 1 and 8. The angiotensin AT2 receptor present on human myometrium membranes displayed a high affinity (pKd = 9.18) and was relatively abundant (53-253 fmol/mg of protein). The pharmacological profile was typical of an angiotensin AT2 receptor with the following order of affinities: (angiotensin III > or = angiotensin II > angiotensin I > PD123319 > angiotensin-(1-7) > angiotensin-(1-6) approximately angiotensin IV >> Losartan). Modifications of the N-terminal side chain and of the primary amine of angiotensin II were evaluated. Neutralisation of the methylcarboxylate (Asp) to a methylcarboxamide (Asn) or to a hydroxymethyl (Ser) or substitution for a methylsulfonate group (cysteic acid) improved the affinity. Extension from methylcarboxylate (Asp) to ethylcarboxylate (Glu) did not affect the affinity. Introduction of larger side chains such as the bulky p-benzoylphenylalanine (p-Bpa) or the positively charged Lys did not substantially affect the affinity. Complete removal of the side chain (angiotensin III), however, resulted in a significant affinity increase. Removal or acetylation of the primary amine of angiotensin II did not noticeably influence the affinity. Progressive alkylation of the primary amine significantly increased the affinity, betain structures being the most potent. It appears that quite important differences exist between the angiotensin AT1 and AT2 receptors concerning their pharmacological profile towards analogues of angiotensin II modified in position 1. On position 8 of angiotensin II, a structure-activity relationship on the angiotensin AT2 receptor was quite similar to that observed with angiotensin AT1 receptor. Bulky, hydrophobic aromatic residues displayed affinities similar to or even better than [Sarcosine1]angiotensin II. Aliphatic residues, especially those of reduced size, caused a significant decrease in affinity especially [Sarcosine1, Gly8]angiotensin II who showed a 30-fold decrease. Introduction of a positive charge (Lys) at position 8 reduced the affinity even further. Stereoisomers in position 8 (L-->D configuration) also induced lower affinities. The angiotensin AT2 receptor display a structure-activity relationship similar to that observed on the AT1 receptor for the C-terminal position of the peptide hormone. Position 1 structure-activity relationships are however fundamentally different between the angiotensin AT1 and AT2 receptor.
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PMID:N- and C-terminal structure-activity study of angiotensin II on the angiotensin AT2 receptor. 957 Apr 82

To identify ligand-binding domains of Angiotensin II (AngII) type 1 receptor (AT1), two different radiolabeled photoreactive AngII analogs were prepared by replacing either the first or the last amino acid of the octapeptide by p-benzoyl-L-phenylalanine (Bpa). High yield, specific labeling of the AT1 receptor was obtained with the 125I-[Sar1,Bpa8]AngII analog. Digestion of the covalent 125I-[Sar1,Bpa8]AngII-AT1 complex with V8 protease generated two major fragments of 15.8 kDa and 17.8 kDa, as determined by SDS-PAGE. Treatment of the [Sar1,Bpa8]AngII-AT1 complex with cyanogen bromide produced a major fragment of 7.5 kDa which, upon further digestion with endoproteinase Lys-C, generated a fragment of 3.6 kDa. Since the 7.5-kDa fragment was sensitive to hydrolysis by 2-nitro-5-thiocyanobenzoic acid, we circumscribed the labeling site of 125I-[Sar1,Bpa8]AngII within amino acids 285 and 295 of the AT1 receptor. When the AT1 receptor was photolabeled with 125I-[Bpa1]AngII, a poor incorporation yield was obtained. Cleavage of the labeled receptor with endoproteinase Lys-C produced a glycopeptide of 31 kDa, which upon deglycosylation showed an apparent molecular mass of 7.5 kDa, delimiting the labeling site of 125I-[Bpa1]AngII within amino acids 147 and 199 of the AT1 receptor. CNBr digestion of the hAT1 I165M mutant receptor narrowed down the labeling site to the fragment 166-199. Taken together, these results indicate that the seventh transmembrane domain of the AT1 receptor interacts strongly with the C-terminal amino acid of [Sar1, Bpa8]AngII interacts with the second extracellular loop of the AT1 receptor.
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PMID:Determination of peptide contact points in the human angiotensin II type I receptor (AT1) with photosensitive analogs of angiotensin II. 1019 64

The p53 tumor suppressor protein preserves genome integrity by regulating growth arrest and apoptosis in response to DNA damage. In response to ionizing radiation (IR), ATM, the gene product mutated in ataxia telangiectasia, stabilizes and activates p53 through phosphorylation of Ser(15) and (indirectly) Ser(20). Here we show that phosphorylation of p53 on Ser(46), a residue important for p53 apoptotic activity, as well as on Ser(9), in response to IR also is dependent on the ATM protein kinase. IR-induced phosphorylation at Ser(46) was inhibited by wortmannin, a phosphatidylinositol 3-kinase inhibitor, but not PD169316, a p38 MAPK inhibitor. p53 C-terminal acetylation at Lys(320) and Lys(382), which may stabilize p53 and activate sequence-specific DNA binding, required Ser(15) phosphorylation by ATM and was enhanced by phosphorylation at nearby residues including Ser(6), Ser(9), and Thr(18). These observations, together with the proposed role of Ser(46) phosphorylation in mediating apoptosis, suggest that ATM is involved in the initiation of p53-dependent apoptosis after IR in human lymphoblastoid cells.
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PMID:ATM mediates phosphorylation at multiple p53 sites, including Ser(46), in response to ionizing radiation. 1187 57

We have previously demonstrated that Chinese hamster ovary (CHO) cells transfected with the angiotensin II AT1 receptor gene containing only the coding region, presented tachyphylaxis to the total inositol phosphate (InsPs) and Ca2+ responses mediated by angiotensin II and [2-lysine]angiotensin II ([Lys2]angiotensin II). Now we have evaluated the possible role of the 3'-untranslated region of the angiotensin AT1 receptor mRNA in modulating the angiotensin AT1 receptor-mediated cellular responses. The binding parameters, as well as the Ca2+ and InsPs responses induced by angiotensin II and [Lys2]angiotensin II were similar in cells transfected with the angiotensin AT1 receptor with or without the 3'-untranslated region sequence. In cells transfected with the receptor containing the 3'-untranslated region sequence, angiotensin II-induced Ca2+ and InsPs responses were desensitized by repeated stimulations, whereas [Lys2]angiotensin II caused desensitization of InsPs production but not of Ca2+ uptake in these cells. Our results suggest that the 3'-untranslated region plays a role in modulating cell signalling involved in the tachyphylaxis of angiotensin AT1 receptor-mediated Ca2+ responses.
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PMID:Angiotensin II-mediated cellular responses: a role for the 3'-untranslated region of the angiotensin AT1 receptor. 1296 45

We have determined that hMOF, the human ortholog of the Drosophila MOF gene (males absent on the first), encoding a protein with histone acetyltransferase activity, interacts with the ATM (ataxia-telangiectasia-mutated) protein. Cellular exposure to ionizing radiation (IR) enhances hMOF-dependent acetylation of its target substrate, lysine 16 (K16) of histone H4 independently of ATM function. Blocking the IR-induced increase in acetylation of histone H4 at K16, either by the expression of a dominant negative mutant DeltahMOF or by RNA interference-mediated hMOF knockdown, resulted in decreased ATM autophosphorylation, ATM kinase activity, and the phosphorylation of downstream effectors of ATM and DNA repair while increasing cell killing. In addition, decreased hMOF activity was associated with loss of the cell cycle checkpoint response to DNA double-strand breaks. The overexpression of wild-type hMOF yielded the opposite results, i.e., a modest increase in cell survival and enhanced DNA repair after IR exposure. These results suggest that hMOF influences the function of ATM.
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PMID:Involvement of human MOF in ATM function. 1592 42


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