Antisera raised to a detergent- and salt-resistant matrix fraction from rat liver
Golgi stacks were used to screen an expression library from rat liver cDNA. A full-length
clone was obtained encoding a protein of 130 kD (termed GM130), the COOH-terminal
domain of which was highly homologous to a Golgi human auto-antigen, golgin-95 (Fritzler
et al., 1993). Biochemical data showed that GM130 is a peripheral cytoplasmic protein
that is tightly bound to Golgi membranes and part of a larger oligomeric complex.
Predictions from the protein sequence suggest that GM130 is an extended rod-like protein
with coiled-coil domains. Immunofluorescence microscopy showed partial overlap with
medial- and trans-Golgi markers but almost complete overlap with the cis-Golgi network
(CGN) marker, syntaxin5. Immunoelectron microscopy confirmed this location showing
that most of the GM130 was located in the CGN and in one or two cisternae on the cis-side
of the Golgi stack. GM130 was not re-distributed to the ER in the presence of brefeldin
A but maintained its overlap with syntaxin5 and a partial overlap with the ER- Golgi
intermediate compartment marker, p53. Together these results suggest that GM130 is
part of a cis-Golgi matrix and has a role in maintaining cis-Golgi structure.