Antisera raised to a detergent- and salt-resistant matrix fraction fro
m rat liver Golgi stacks were used to screen an expression library fro
m 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 tha
t GM130 is an extended rod-like protein with coiled-coil domains, Immu
nofluorescence microscopy showed partial over-lap with medial- and tra
ns-Golgi markers but almost complete overlap with the cis-Golgi networ
k (CGN) marker, syntaxin5, Immunoelectron microscopy confirmed this lo
cation showing that most of the GM130 was located in the CGN and in on
e or two cisternae on the cis-side of the Golgi stack. GM130 was not r
e-distributed to the ER in the presence of brefeldin A but maintained
its overlap with syntaxin5 and a partial overlap with the ER-Golgi int
ermediate 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.