Targeting of chimeric Gαi proteins to specific membrane domains

• Autor(a) principal: Almeida, Jose Bruno de
• Data de Publicação: 1994
• Outros Autores: Holtzman, Eliezer J., Peters, Philip, Ercolani, Louis, Ausiello, Dennis A., Stow, Jennifer L.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional da UFRN
• Texto Completo: https://repositorio.ufrn.br/handle/123456789/54378
• topic: targeting signal; g protein; plasma membrane; immunofluorescence; golgi

Heterotrimeric guanine nucleotide-regulatory (G) proteins are associated with a variety of intracellular membranes and specific plasma membrane domains. In polarized epithelial LLC-PK1 cells we have shown previously that endogenous Gαi-2 is localized on the basolateral plasma membrane, whereas Gαi-3 is localized on Golgi membranes. The targeting of these highly homologous Gαi proteins to distinct membrane domains was studied by the transfection and expression of chimeric Gαi proteins in LLC-PK1 cells. Chimeric cDNAs were constructed from the cDNAs for Gαi-3 and Gαi-2 and introduced into a pMXX eukaryotic expression vector containing a mouse metallothioneinI promotor. Stably transfected cell lines were produced that expressed either Gαi-2/3 or Gαi-3/2 chimeric proteins. Chimeric and endogenous Gαi proteins were detected in cells using specific carboxy-terminal peptide antibodies. Immunofluorescence staining was used to localize endogenous and chimeric Gαi proteins in LLC-PK1 cells. The staining of chimeric proteins was detected as an increased intensity of staining on membranes containing endogenous Gαi proteins. Using confocal microscopy and image analysis we localized Gαi-2 to a specific sub-domain of the lateral membrane of polarized cells, the chimeric Gαi-3/2 protein was then shown to colocalize with endognenous Gαi-2 in the same lateral plasma membrane domain. The chimeric Gαi-2/3 protein colocalized with endogenous Gαi-3 on Golgi membranes in LLC-PK1 cells. These results show that chimeric Gαi proteins were targeted to the same membrane domains as endogenous Gαi proteins and the specificity of their membrane targeting was conferred by the carboxy-terminal end of the proteins. These data provide the first evidence for specific targeting information contained in the carboxy termini of Gαi proteins, which appears to be independent of amino-terminal membrane attachment sites in these proteins