RESUMO
The mechanism by which high concentrations of cAMP selectively destabilize the gp80 mRNA in Dictyostelium discoideum was investigated. This treatment which leads to down-regulation of the cAMP receptor was also found to cause an increase in calcium uptake. Given this observation, we sought a role for calcium as a second messenger in the degradation of the gp80 mRNA. Changes in the mRNA levels were examined after treating cells with compounds known to alter their intracellular Ca2+ concentrations. This included the use of A23187, Ca2+, 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate HC1 (TMB-8), LiCl and 8-p-chlorophenylthioadenosine 3',5'-cyclic monophosphate (ClPhS-Ado-3':5'-P). The sum of the data suggest that it is the cAMP-induced influx of Ca2+ across the plasma membrane, as apposed to a cAMP-mediated release of Ca2+ from intracellular stores, that initiates gp80 mRNA degradation. Treatment of cells with Concanavalin A (ConA) to induce cAMP receptor down-regulation, also causes a reduction in gp80 mRNA levels and an increase in calcium uptake.
Assuntos
Cálcio/metabolismo , Moléculas de Adesão Celular/genética , Dictyostelium/genética , Proteínas de Protozoários , RNA Mensageiro/metabolismo , Receptores de AMP Cíclico/fisiologia , Animais , Calcimicina/farmacologia , Concanavalina A/farmacologia , Dictyostelium/citologia , Regulação para Baixo , Proteínas Fúngicas/genética , Ácido Gálico/análogos & derivados , Ácido Gálico/farmacologia , Regulação Fúngica da Expressão Gênica/genética , Cloreto de Lítio/farmacologia , Glicoproteínas de Membrana/genética , Glicoproteínas de Membrana/metabolismo , RNA Mensageiro/efeitos dos fármacosAssuntos
Humanos , Animais , Gatos , Bovinos , Cães , Ratos , Neuroanatomia/tendências , Estimulação Química , Neurotransmissores , Receptores de Neurotransmissores/química , Transmissão Sináptica/fisiologia , Terminações Nervosas/fisiologia , Terminações Nervosas/química , Neurotransmissores/classificação , Neurotransmissores/fisiologia , Receptores Adrenérgicos/fisiologia , Receptores Adrenérgicos/química , Receptores Colinérgicos/fisiologia , Receptores Colinérgicos/química , Receptores de AMP Cíclico/fisiologia , Receptores de AMP Cíclico/químicaAssuntos
Humanos , Animais , Gatos , Bovinos , Cães , Ratos , Receptores de Neurotransmissores/química , Transmissão Sináptica/fisiologia , Neurotransmissores , Neuroanatomia/tendências , Estimulação Química , Neurotransmissores/classificação , Neurotransmissores/fisiologia , Terminações Nervosas/fisiologia , Terminações Nervosas/química , Receptores Adrenérgicos/fisiologia , Receptores Adrenérgicos/química , Receptores Colinérgicos/fisiologia , Receptores Colinérgicos/química , Receptores de AMP Cíclico/fisiologia , Receptores de AMP Cíclico/químicaRESUMO
We have studied the cell differentiation of Trypanosoma cruzi in an vitro system that allows the transformation of epimastigotes into metacyclic trypomastigotes. Intracellular cAMP levels of epimastigotes increased 3 fold prior to their differentiation into metacyclics where cAMP remained elevated 3.7 fold with respect to epimastigotes. We also observed a 3 fold increase in the specific activity of cAMP-binding of metacyclics crude homogenates. This activity resided in a cAMP-binding receptor protein (CARPT) which was different from the typical cAMP-binding subunits (RI and RII) of cAMP-dependent protein kinases, as shown by the use of polyclonal antibodies prepared against these two types of proteins. Anti-RI antibodies did not react with CARPT, and anti-RII antibodies gave a cross reaction with CARPT which was at least 1,000 fold less sensitive than the one shown by the homologous antigen. On Western blots CARPT displayed a major band with Mr = 87,000 instead of Mr = 56,000 for RII. These studies implicate that cAMP may act as a mediator of the cell differentiation of T. cruzi by a mechanism involving a novel type of cAMP-binding receptor.