Phosphorylation of the polymeric immunoglobulin receptor required for its efficient transcytosis
Article Abstract:
Epithelial cells, like all cells, are composed of a cell membrane surrounding cytoplasm and a cell nucleus. The membrane has two regions, an apical and a basolateral, with different protein compositions. In one type of epithelial cell (MDCK cells), approximately one-half of the cell surface is internalized by the cell in the process known as endocytosis, forming vesicles called endosomes (endocytotic vesicles). This process is ongoing in virtually all cells, resulting in a more or less constant recycling of membrane proteins and other material. Endosomes contain these substances, which are subsequently directed to different locations within the cell. Understanding how such intracellular 'traffic' is regulated is of interest; in particular, how polarity is maintained in the epithelial cell has implications for the cell's function. Transcytosis is the process whereby material is moved across the cell, and one cell-surface receptor protein, the polymeric immunoglobulin receptor (pIgR), which normally moves across the cell, was studied to gain insight into this process. pIgR transports two immunoglobulins (antibody molecules), IgA and IgM, from the basolateral cell surface to the apical surface. The pIgR-immunoglobulin complex moves from the endosome to transcytotic vesicles, in which it moves across the cell. What directs pIgR into the transcytotic pathway? Studies were performed at different stages of the transport process, and results showed that phosphorylation (addition of a phosphate group) of pIgR at a particular place in its structure (position 664, a serine residue) is necessary for efficient transcytosis. Phosphorylation acts like a molecular 'switch' to regulate transcytosis. The process may also be important in transport of other membrane receptor proteins. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: Science
Subject: Science and technology
ISSN: 0036-8075
Year: 1990
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HIV's Early Home And Inner Life
Article Abstract:
The Colloquium of the Lemanique Center for AIDS Research held its first conference in Lausanne, Switzerland. 230 HIV and AIDS researchers gathered to discuss the latest in AIDS-related research. Topics included the structure and life cycle of HIV, and the importance of targeting T lymphocytes in early infection.
Publication Name: Science
Subject: Science and technology
ISSN: 0036-8075
Year: 1998
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