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CD39 Reveals Novel Insights into the Role of Transmembrane Domains in Protein Processing, Apical Targeting and Activity
Author(s) -
Papanikolaou Agathi,
Papafotika Alexandra,
Christoforidis Savvas
Publication year - 2011
Publication title -
traffic
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.677
H-Index - 130
eISSN - 1600-0854
pISSN - 1398-9219
DOI - 10.1111/j.1600-0854.2011.01224.x
Subject(s) - endoplasmic reticulum , biology , microbiology and biotechnology , transmembrane protein , golgi apparatus , protein targeting , membrane protein , transmembrane domain , transport protein , protein sorting signals , signal peptide , biochemistry , membrane , peptide sequence , receptor , gene
Cargo proteins of the biosynthetic secretory pathway are folded in the endoplasmic reticulum (ER) and proceed to the trans Golgi network for sorting and targeting to the apical or basolateral sides of the membrane, where they exert their function. These processes depend on diverse protein domains. Here, we used CD39 (NTPdase1), a modulator of thrombosis and inflammation, which contains an extracellular and two transmembrane domains (TMDs), as a model protein to address comprehensively the role of native TMDs in folding, polarized transport and biological activity. In MDCK cells, CD39 exits Golgi dynamin‐dependently and is targeted to the apical side of the membrane. Although the N‐terminal TMD possesses an apical targeting signal, the N‐ and C‐terminal TMDs are not required for apical targeting of CD39. Folding and transport to the plasma membrane relies only on the C‐terminal TMD, while the N‐terminal one is redundant. Nevertheless, both N‐ and C‐terminal anchoring as well as genuine TMDs are critical for optimal enzymatic activity and activation by cholesterol. We conclude therefore that TMDs are not just mechanical linkers between proteins and membranes but are also able to control folding and sorting, as well as biological activity via sensing components of lipid bilayers.