Distribution of G-proteins in rat liver plasma-membrane domains and endocytic pathways

Ali, Nawab, Milligan, Graeme and Evans, William Howard 1989. Distribution of G-proteins in rat liver plasma-membrane domains and endocytic pathways. Biochemical Journal 261 (3) , pp. 905-912.

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Abstract

1. The distribution of the alpha- and beta-subunits of nucleotide-binding G-proteins among rat liver sinusoidal, lateral and canalicular plasma membranes, endosomes, Golgi membranes and lysosomes was investigated. 2. Pertussis-toxin-catalysed ADP-ribosylation identified a 41 kDa inhibitory alpha-subunit in all liver plasma-membrane functional domains as well as in endosomes. An antibody to a synthetic peptide corresponding to a C-terminal sequence of the inhibitory alpha-subunit also identified the 41 kDa polypeptide in all plasma-membrane domains, in 'early' and 'late' endosomes and in Golgi membranes; this polypeptide was not detected in lysosomes. The antibody-binding studies showed that bile-canalicular plasma membranes had the highest content of the inhibitory alpha-subunit. 3. Immunofluorescent microscopy confirmed the presence of the inhibitory alpha-subunit in all regions of the hepatocyte's cell surface. 4. An antibody recognizing the beta-subunit showed that a 36 kDa polypeptide was present in all plasma membranes and in 'early' and 'late' endosomes; it was not detected in lysosomes. The relative distribution among the fractions of this polypeptide was similar to the distribution of the inhibitory alpha-subunit. 5. The presence of high levels of the G-protein inhibitory alpha-subunit in bile-canalicular plasma membranes was confirmed by demonstration of its co-fractionation with marker enzymes in Nycodenz gradients and by free-flow electrophoresis. The significance of this location is discussed.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Medicine
Subjects:	R Medicine > R Medicine (General)
Publisher:	Biochemical Society
ISSN:	0264-6021
Last Modified:	17 Mar 2021 02:57
URI:	https://orca.cardiff.ac.uk/id/eprint/66811

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