Conformational Defects Slow Golgi Exit, Block Oligomerization, and Reduce Raft Affinity of Caveolin-1 Mutant Proteins
Protein Synthesis Inhibitors
0303 health sciences
Protein Conformation
Caveolin 1
Molecular Sequence Data
Golgi Apparatus
Protein Sorting Signals
Caveolins
Cell Line
Protein Transport
03 medical and health sciences
Membrane Microdomains
Mutation
Medicine and Health Sciences
Animals
Amino Acid Sequence
Cycloheximide
Biomarkers
DOI:
10.1091/mbc.e04-06-0480
Publication Date:
2004-08-11T01:23:51Z
AUTHORS (6)
ABSTRACT
Caveolin-1, a structural protein of caveolae, is cleared unusually slowly from the Golgi apparatus during biosynthetic transport. Furthermore, several caveolin-1 mutant proteins accumulate in the Golgi apparatus. We examined this behavior further in this mutant study. Golgi accumulation probably resulted from loss of Golgi exit information, not exposure of cryptic retention signals, because several deletion mutants accumulated in the Golgi apparatus. Alterations throughout the protein caused Golgi accumulation. Thus, most probably acted indirectly, by affecting overall conformation, rather than by disrupting specific Golgi exit motifs. Consistent with this idea, almost all the Golgi-localized mutant proteins failed to oligomerize normally (even with an intact oligomerization domain), and they showed reduced raft affinity in an in vitro detergent-insolubility assay. A few mutant proteins formed unstable oligomers that migrated unusually slowly on blue native gels. Only one mutant protein, which lacked the first half of the N-terminal hydrophilic domain, accumulated in the Golgi apparatus despite normal oligomerization and raft association. These results suggested that transport of caveolin-1 through the Golgi apparatus is unusually difficult. The conformation of caveolin-1 may be optimized to overcome this difficulty, but remain very sensitive to mutation. Disrupting conformation can coordinately affect oligomerization, raft affinity, and Golgi exit of caveolin-1.
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