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General Comment |
The Golgi apparatus, which participates in glycosylation and transport of proteins and lipids in the secretory pathway,
consists of a series of stacked cisternae (flattened membrane sacs). Interactions between the Golgi and microtubules are
thought to be important for the reorganization of the Golgi after it fragments during mitosis. Giantin is an integral protein in the Golgi.
Sohda M, et al reported the identification and characterization of a novel Golgi protein, GCP60, that
interacts with the integral membrane protein giantin.
They previously demonstrated that the integral membrane protein giantin has the Golgi
localization signal at the COOH-terminal cytoplasmic domain. In the present study, using
this domain as a bait in the yeast two-hybrid screening system, they identified a novel protein
interacting with giantin. The 3.6-kb mRNA encoding a 528-amino-acid protein of 60 kDa
(designated as GCP60) was ubiquitously expressed, especially abundant in the testis and ovary.
Immunofluorescence and immunoelectron microscopy confirmed that GCP60 was co-localized
with giantin in the Golgi complex. GCP60 was found to be a peripheral protein associated with
the Golgi membrane, where the COOH-terminal domain of GCP60 interacts with the
COOH-terminal cytoplasmic domain of giantin. Overexpression of the COOH-terminal domain
of GCP60 caused disassembly of the Golgi structure and blocked protein transport from the
endoplasmic reticulum to the Golgi. Taken together, these results suggest that GCP60 is involved
in the maintenance of the Golgi structure by interacting with giantin, affecting protein transport
between the endoplasmic reticulum and the Golgi.
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