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Hsp70 Associates with Lipid Membranes as Part of the Extracellular Export Mechanism
Author(s) -
De Maio Antonio,
Lopez Victor,
Armijo Gabrielle,
Cauvi David,
Arispe Nelson
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.886.2
Subject(s) - hsp70 , cytosol , microbiology and biotechnology , extracellular , heat shock protein , chemistry , membrane , chaperone (clinical) , lipid bilayer , biochemistry , biology , enzyme , medicine , pathology , gene
The universal response to stress is mediated by the expression of heat shock proteins (hsp). The cytoprotective effect of hsp has been associated with hsp's chaperone function within the cytosol. However, they are also exported outside cells where they act as a systemic response to stress. Hsp70, the major inducible member of the hsp family, does not contain any consensus secretory signal that predicts its export via the classical ER‐Golgi, secretory pathway. It appears to translocate from the cytosol directly to the extracellular milieu. We propose that the insertion of Hsp70 into the plasma membrane is the first step in the export process. We investigated the mechanism of Hsp70 membrane insertion using a liposome assay. It was observed that Hsp70 insertion into lipid membranes was spontaneous and specific for negatively charged lipids, such as phosphatidylserine. Hsp70 also has a preference for less fluid lipid environments. The region of the protein that is inserted into the lipid bilayer was mapped toward the C‐terminus end of the molecule by a proteomic approach. Finally, Hsp70 was found in oligomeric forms upon membrane insertion, which may explain its ion channel activity.