
A novel receptor function for the heat shock protein Grp78: silencing of Grp78 gene expression attenuates alpha2M*-induced signalling.
The activated proteinase inhibitor alpha2-macroglobulin (alpha2M*) binds to two receptors, the low density lipoprotein receptor-related protein (LRP-1) and the alpha2M* signalling receptor (alpha2MSR). Silencing LRP-1 gene expression in macrophages by RNA interference does not block alpha2M* activation of signalling cascades. We now demonstrate that transfection of macrophages with a double-stranded RNA homologous in sequence to the Grp78 gene markedly decreased induction of inositol 1,4,5-trisphosphate (IP3) and subsequent IP3-dependent elevation of [Ca2+]i induced by alpha2M*. Concomitantly, alpha2M*-induced increase in [3H]thymidine uptake was abolished in these transfected cells. Insulin treatment significantly upregulates alpha2MSR and it also caused a marked increase in Grp78 expression which could be blocked by RNA interference. alpha2M* treatment of cells activates the Ras- and PI 3-kinase-dependent signalling pathways. Suppressing Grp78 expression leads to the loss of these activation events in transfected macrophages. We thus conclude that Grp78 is the alpha2M* signalling receptor.
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Related Subject Headings
- alpha-Macroglobulins
- Signal Transduction
- RNA, Double-Stranded
- RNA Interference
- Phosphatidylinositol 3-Kinases
- Molecular Chaperones
- Mice
- Macrophages, Peritoneal
- Low Density Lipoprotein Receptor-Related Protein-1
- Insulin
Citation

Published In
DOI
ISSN
Publication Date
Volume
Issue
Start / End Page
Location
Related Subject Headings
- alpha-Macroglobulins
- Signal Transduction
- RNA, Double-Stranded
- RNA Interference
- Phosphatidylinositol 3-Kinases
- Molecular Chaperones
- Mice
- Macrophages, Peritoneal
- Low Density Lipoprotein Receptor-Related Protein-1
- Insulin