Expressão do receptor sensor de calcio com mutações e deleção no dominio extracelular

AUTOR(ES)
DATA DE PUBLICAÇÃO

2004

RESUMO

The calcium sensing receptor (CASR) is a member of the family III of G protein coupled receptors and plays an essential role in calcium homeostasis. The extracellular domain (ECD) of the receptor is the most important site for Ca/+-binding and the majority of the naturally occurring mutations in the ECD affects only the affinity of the receptor for Cao2+. Other mutations in the ECD could result in a more gross alteration of the receptor structure, reflected by reducing expression levels of the receptor at the cell surface. The objective of this thesis was to investigate the expression levels of the CASR with mutations in the extracellular domain where activating and inactivating mutations have been described. The mutation resulted in changes in aminoacid polarity or acid/base character. In addition, a deletion of a region between 139 and 167 aminoacids of the extracelullar domain of the CASR, a highly hydrophobic region, was perform to investigate its relevance. The Western blotting technique demonstrated that alI mutant receptors were expressed in HEK-293 cells. Analysis of the intensity of the bands by densitometry in three separate experiments showed no significant differences in expression levels of the mutants Al16T, Nl18S, E127K, F128Y, T138K and ~139-167 compared to the CASR wild type. The mutant receptor P55S showed a drastically decreased expression leveI in the dimeric and oligomeric forms (-220 kDa) when compared to the CASR wild type. In conclusion, the expression of the CASR could be affected by alterations of the amino acids characteristics (polarity, acid/base character) and the changes in the expression levels is dependent on the position of mutated amino acid. The position 55 is critica! for expression of the dimeric forms of the receptor, while the hydrophobic region between 139 and 167 amino acids is not important for the expression nor the dimerization of the CASR

ASSUNTO(S)

calcio no organismo calcio (bioquimica) mutação (biologia)

ACESSO AO ARTIGO

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