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1.
Biochem Biophys Res Commun ; 405(1): 122-7, 2011 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-21216233

RESUMO

FFA2 (GPR43) is a receptor for short-chain fatty acids (SCFAs), acetate, and propionate. FFA2 is predominantly expressed in islets, a subset of immune cells, adipocytes, and the gastrointestinal tract which suggest a possible role in inflammatory and metabolic conditions. We have previously described the identification and characterization of novel phenylacetamides as allosteric agonists of FFA2. In the current study, we have investigated the molecular determinants contributing to receptor activation with the endogenous and synthetic ligands as well as allosteric interactions between these two sites. The mutational analysis revealed previously unidentified sites that may allosterically regulate orthosteric ligand's function as well as residues potentially important for the interactions between orthosteric and allosteric binding sites.


Assuntos
Receptores de Superfície Celular/agonistas , Receptores de Superfície Celular/genética , Regulação Alostérica , Animais , Sítios de Ligação , Análise Mutacional de DNA , Células HEK293 , Humanos , Ligantes , Mutagênese , Conformação Proteica , Receptores de Superfície Celular/química
2.
Mol Pharmacol ; 74(6): 1599-609, 2008 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-18818303

RESUMO

FFA2 (GPR43) has been identified as a receptor for short-chain fatty acids (SCFAs) that include acetate and propionate. FFA2 is highly expressed in islets, a subset of immune cells, and adipocytes. Although the potential roles of FFA2 activation in these tissues have previously been described, the physiological functions are still unclear. The potency for SCFAs on FFA2 is low, in the high micromolar to millimolar concentrations. To identify better pharmacological tools to study receptor function, we used high-throughput screening (HTS) to discover a series of small molecule phenylacetamides as novel and more potent FFA2 agonists. This series is specific for FFA2 over FFA1 (GPR40) and FFA3 (GPR41), and it is able to activate both the Galpha(q) and Galpha(i) pathways in vitro on Chinese hamster ovary cells stably expressing FFA2. Treatment of adipocytes with these compounds also resulted in Galpha(i)-dependent inhibition of lipolysis similar to that of endogenous ligands (SCFAs). It is noteworthy that these compounds not only acted as FFA2 agonists but also exhibited positive cooperativity with acetate or propionate. The observed allosteric modulation was consistent in all the functional assays that we have explored, including cAMP, calcium mobilization, guanosine 5'-[gamma-thio]triphosphate binding, and lipolysis. Molecular modeling analysis of FFA2 based on human beta(2)-adrenergic receptor structure revealed potential nonoverlapping binding sites for the endogenous and synthetic ligands, further providing insight into the binding pocket for the allosteric interactions. This is the first report describing the identification of novel allosteric modulators with agonist activity for FFA2, and these compounds may serve as tools for further unraveling the physiological functions of the receptor and its involvement in various diseases.


Assuntos
Benzenoacetamidas/farmacologia , Receptores de Superfície Celular/agonistas , Tiazóis/farmacologia , Células 3T3-L1 , Adipócitos/efeitos dos fármacos , Adipócitos/metabolismo , Regulação Alostérica , Sequência de Aminoácidos , Animais , Benzenoacetamidas/química , Células CHO , Cricetinae , Cricetulus , Humanos , Ligantes , Lipólise/efeitos dos fármacos , Camundongos , Modelos Moleculares , Dados de Sequência Molecular , Ensaio Radioligante , Relação Estrutura-Atividade , Tiazóis/química
3.
PLoS One ; 12(7): e0180190, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28727837

RESUMO

Inflammatory bowel disease (IBD) is associated with a loss of intestinal barrier function and dysregulated immune responses. It has been shown that short chain fatty acids (SCFAs) are protective in IBD and that GPR43 mediates the protective effects of SCFAs. In this study, we investigated the effects of SCFAs in comparison to highly specific GPR43 agonists on human intestinal epithelial and immune cells. Our results confirm that SCFAs are enhancers of barrier function in intestinal epithelial cells. Additionally, SCFAs also displayed potent immunoregulatory properties based upon the ability to inhibit LPS-induced cytokine production in PBMC, and human T cell proliferation and cytokine production. Unexpectedly, and in contrast to the current belief, specific GPR43 agonists failed to exhibit similar barrier enhancing and anti-inflammatory properties. These findings demonstrate that SCFA possess broad protective functions in IBD and agonizing GPR43 alone is unlikely to be beneficial in patients.


Assuntos
Células Epiteliais/efeitos dos fármacos , Mucosa Intestinal/efeitos dos fármacos , Receptores de Superfície Celular/agonistas , Animais , Células CACO-2 , Linhagem Celular , Proliferação de Células/efeitos dos fármacos , Citocinas/metabolismo , Células Epiteliais/imunologia , Células Epiteliais/metabolismo , Ácidos Graxos Voláteis , Humanos , Mucosa Intestinal/imunologia , Mucosa Intestinal/metabolismo , Leucócitos Mononucleares/efeitos dos fármacos , Leucócitos Mononucleares/imunologia , Leucócitos Mononucleares/metabolismo , Camundongos
4.
ACS Med Chem Lett ; 6(1): 68-72, 2015 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-25589933

RESUMO

The kinase/endonuclease inositol requiring enzyme 1 (IRE1α), one of the sensors of unfolded protein accumulation in the endoplasmic reticulum that triggers the unfolded protein response (UPR), has been investigated as an anticancer target. We identified potent allosteric inhibitors of IRE1α endonuclease activity that bound to the kinase site on the enzyme. Structure-activity relationship (SAR) studies led to 16 and 18, which were selective in kinase screens and were potent against recombinant IRE1α endonuclease as well as cellular IRE1α. The first X-ray crystal structure of a kinase inhibitor (16) bound to hIRE1α was obtained. Screening of native tumor cell lines (>300) against selective IRE1α inhibitors failed to demonstrate any effect on cellular viability. These results suggest that IRE1α activity is not essential for viability in most tumor cell lines, in vitro, and that interfering with the survival functions of the UPR may not be an effective strategy to block tumorigenesis.

6.
FEBS Lett ; 584(19): 4208-14, 2010 Oct 08.
Artigo em Inglês | MEDLINE | ID: mdl-20837008

RESUMO

FFAR2 (GPR43) is a receptor for short-chain fatty acids (SCFAs), acetate and propionate. In the current study, we investigate the molecular determinants contributing to receptor activation by endogenous ligands. Mutational analysis revealed several important residues located in transmembrane domains (TM) 3, 4, 5, 6, and 7 for acetate binding. Interestingly, mutations that abolished acetate activity, including the mutation in the well-conserved D(E)RY motif, could be rescued by a recently identified synthetic allosteric agonist. These findings provide additional insight into agonist binding and activation which may aid in designing allosteric ligands for targeting receptor function in various diseases.


Assuntos
Receptores de Superfície Celular/química , Receptores de Superfície Celular/genética , Acetamidas/farmacologia , Ácido Acético/metabolismo , Regulação Alostérica , Sítio Alostérico/genética , Motivos de Aminoácidos , Humanos , Técnicas In Vitro , Cinética , Ligantes , Modelos Moleculares , Mutagênese Sítio-Dirigida , Proteínas Mutantes/agonistas , Proteínas Mutantes/química , Proteínas Mutantes/genética , Proteínas Mutantes/metabolismo , Receptores de Superfície Celular/agonistas , Receptores de Superfície Celular/metabolismo , Proteínas Recombinantes/agonistas , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo
7.
Can J Microbiol ; 54(4): 241-7, 2008 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-18388996

RESUMO

The cryptic plasmid (pAT) of Agrobacterium tumefaciens was not required for virulence or attachment to plant surfaces. However, mutations in the attC and attG genes located on pAT caused the bacteria to become avirulent and non-attaching on tomato, carrot, and Bryophyllum daigremontiana. This was the case whether the mutation was in the copy of the genes located on pAT or whether it was carried in a second copy of the attA-G operon located on a plasmid in cells that contained a wild-type copy of pAT. Thus attC and attG mutations are dominant negative mutations. The mechanism by which these mutations block attachment and virulence is unknown.


Assuntos
Transportadores de Cassetes de Ligação de ATP/genética , Agrobacterium tumefaciens/patogenicidade , Aderência Bacteriana , Proteínas de Bactérias/genética , Mutação , Tumores de Planta/microbiologia , Agrobacterium tumefaciens/genética , Agrobacterium tumefaciens/fisiologia , Daucus carota/microbiologia , Genes Dominantes , Solanum lycopersicum/microbiologia , Óperon , Raízes de Plantas/microbiologia , Plasmídeos , Virulência
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