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Abstract
The endoplasmic reticulum (ER) consists of tubules that are shaped by the reticulons
and DP1/Yop1p, but how the tubules form an interconnected network is unknown. Here,
we show that mammalian atlastins, which are dynamin-like, integral membrane GTPases,
interact with the tubule-shaping proteins. The atlastins localize to the tubular ER
and are required for proper network formation in vivo and in vitro. Depletion of the
atlastins or overexpression of dominant-negative forms inhibits tubule interconnections.
The Sey1p GTPase in S. cerevisiae is likely a functional ortholog of the atlastins;
it shares the same signature motifs and membrane topology and interacts genetically
and physically with the tubule-shaping proteins. Cells simultaneously lacking Sey1p
and a tubule-shaping protein have ER morphology defects. These results indicate that
formation of the tubular ER network depends on conserved dynamin-like GTPases. Since
atlastin-1 mutations cause a common form of hereditary spastic paraplegia, we suggest
ER-shaping defects as a neuropathogenic mechanism.