A heterotrimeric GProtein, G«i-3 , on Golgi membranes regulates the secretion of a heparan sulfate proteoglycan in LLC-PKI epithelial cells

• Autor(a) principal: Almeida, Jose Bruno de
• Data de Publicação: 1991
• Outros Autores: Stow, Jennifer L., Narula, Navneet, Holtzman, Eliezer J., Ercolani, Louis, Ausiello, Dennis A.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional da UFRN
• Texto Completo: https://repositorio.ufrn.br/handle/123456789/54389; https://doi.org/10.1083/jcb.114.6.1113
• topic: heterotrimeric G protein; golgi

A heterotrimeric Gai subunit, «i- 3 , is localized on Golgi membranes in LLC-PKI and NRK epithelial cells where it colocalizes with mannosidase II by immunofluorescence . The M-3 was found to be localized on the cytoplasmic face of Golgi cisternae and it was distributed across the whole Golgi stack. The a;_3 subunit is found on isolated rat liver Golgi membranes by Western blotting and Gai -3 on the Golgi apparatus is ADP ribosylated by pertussis toxin. LLCPKI cells were stably transfected with GO;-3 on an MT1, inducible promoter in order to overexpress ai-3 on Golgi membranes. The intracellular processing and constitutive secretion of the basement membrane heparan sulfate proteoglycan (HSPG) was measured in LLC-PK, cells. Overexpression of ai-3 on Golgi membranes in transfected cells retarded the secretion of HSPG and accumulated precursors in the medial-trans-Golgi . This effect was reversed by treatment of cells with pertussis toxin which results in ADP-ribosylation and functional uncoupling of Gai-3 on Golgi membranes. These results provide evidence for a novel role for the pertussis toxin sensitive Gai-3 protein in Golgi trafficking of a constitutively secreted protein in epithelial cells