Abstract
The Golgi apparatus is an intracellular compartment necessary for post-translational modification, sorting and transport of proteins. It plays a key role in mitotic entry through the Golgi mitotic checkpoint. In order to identify new proteins involved in the Golgi mitotic checkpoint, we combine the results of a knockdown screen for mitotic phenotypes and a localization screen. Using this approach, we identify a new Golgi protein C11ORF24 (NP_071733.1). We show that C11ORF24 has a signal peptide at the N-terminus and a transmembrane domain in the C-terminal region. C11ORF24 is localized on the Golgi apparatus and on the trans-Golgi network. A large part of the protein is present in the lumen of the Golgi apparatus whereas only a short tail extends into the cytosol. This cytosolic tail is well conserved in evolution. By FRAP experiments we show that the dynamics of C11ORF24 in the Golgi membrane are coherent with the presence of a transmembrane domain in the protein. C11ORF24 is not only present on the Golgi apparatus but also cycles to the plasma membrane via endosomes in a pH sensitive manner. Moreover, via video-microscopy studies we show that C11ORF24 is found on transport intermediates and is colocalized with the small GTPase RAB6, a GTPase involved in anterograde transport from the Golgi to the plasma membrane. Knocking down C11ORF24 does not lead to a mitotic phenotype or an intracellular transport defect in our hands. All together, these data suggest that C11ORF24 is present on the Golgi apparatus, transported to the plasma membrane and cycles back through the endosomes by way of RAB6 positive carriers.
Highlights
The Golgi complex plays a central role in multiple functions essential for cell growth, homeostasis and division
BLASTS, sequence motif and homology searches led us to the identification of three interesting domains: a signal peptide, a transmembrane domain and a cytosolic tail
The entire sequence of Homo Sapiens (Hs) C11ORF24 was aligned with its potential homologues in Mus musculus (Mm) and Dano rerio (Dr) using Clustal W2 [13,14] (Figure 1B)
Summary
The Golgi complex plays a central role in multiple functions essential for cell growth, homeostasis and division. It processes and sorts proteins and lipids synthesized in the endoplasmic reticulum and connects the anterograde and retrograde trafficking pathways. The Golgi apparatus is composed of stacks of flat cisternae. Each stack exhibits an internal polarity: the cis part exchanges material with the endoplasmic reticulum through the intermediate compartment whereas, at the other extremity the trans-Golgi separated from the cis-Golgi by medial cisternae is in contact with the transGolgi network (TGN). The TGN is responsible for the final sorting steps that target several different destinations and exchanges material with the endocytic compartments
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