A heterotrimeric G protein, Gαi-3, on Golgi membranes regulates the secretion of a heparan sulfate proteoglycan in LLC-PK1 epithelial cells

Renal Unit, Massachusetts General Hospital, Boston.
The Journal of Cell Biology (Impact Factor: 9.83). 10/1991; 114(6):1113-24.
Source: PubMed


A heterotrimeric G alpha i subunit, alpha i-3, is localized on Golgi membranes in LLC-PK1 and NRK epithelial cells where it colocalizes with mannosidase II by immunofluorescence. The alpha i-3 was found to be localized on the cytoplasmic face of Golgi cisternae and it was distributed across the whole Golgi stack. The alpha i-3 subunit is found on isolated rat liver Golgi membranes by Western blotting and G alpha i-3 on the Golgi apparatus is ADP ribosylated by pertussis toxin. LLC-PK1 cells were stably transfected with G alpha i-3 on an MT-1, inducible promoter in order to overexpress alpha i-3 on Golgi membranes. The intracellular processing and constitutive secretion of the basement membrane heparan sulfate proteoglycan (HSPG) was measured in LLC-PK1 cells. Overexpression of alpha i-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 G alpha i-3 on Golgi membranes. These results provide evidence for a novel role for the pertussis toxin sensitive G alpha i-3 protein in Golgi trafficking of a constitutively secreted protein in epithelial cells.

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    • "the control of membrane trafficking and regulate exocytosis from intracellular organelles (Stow et al., 1991; Aridor et al., 1993). In addition, G proteins of the Gi family have been reported to control the trafficking of aquaporin 2 channels in kidney epithelial cells (Valenti et al., 1998), and also the trafficking and distribution of connexin 43 hemichannels in Novikoff hepatoma cells (Lampe et al., 2001). "

    Full-text · Article · Sep 2015 · The Journal of General Physiology
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    • "Molecular Biology of the Cell homeostasis. In pharmacological studies, Golgi-localized Gβγ was shown to be required for post-Golgi anterograde transport (Stow et al., 1991; Irannejad and Wedegaertner, 2010). However, the GPCRs associated with Golgi-localized Gβγ are not known. "
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    Full-text · Article · Jul 2015 · Molecular biology of the cell
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    • "Heterotrimeric G proteins were detected in the Golgi over two decades ago (Barr et al., 1992; Stow et al., 1991), and numerous studies have provided clues that they may regulate membrane traffic and maintain the structural integrity of the Golgi (Cancino and Luini, 2013). However, the concept of G protein activation at the Golgi and the potential impact of such activation are met with skepticism, primarily due to the lack of direct proof of G protein activation. "
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