Description of Research Expertise

Research Interests

Functions of molecular chaperones in modulating cell surface receptors and secreted proteins

Key words: Chaperones, BiP, GRP94, HSP90, calreticulin, Amyloid, Light Chain, Heavy Chain, B Cell Receptor, Insulin-like growth factors, Peptide, Stress Response, Development.

Description of Research

Communication among cells through secreted ligands and their receptors underlies the organization of tissues. The proper expression of receptors and secretion of protein ligands are dependent on accessory proteins, molecular chaperones, which regulate their biosynthesis and minimize their misfolding. Our work focuses on the molecular chaperones in the endoplasmic reticulum, where membrane and secreted proteins are synthesized.

BiP is a peptide binding protein that controls folding of antigen receptors by binding selectively to some peptides in the newly synthesized proteins. Because of this ability, BiP provides an important quality control function in screening somatically mutated molecules. One project in the lab concerns how BiP recognizes normal Ig sequences and distinguishes them from aggregation-prone somatic mutants. A second project examines the use of BiP as an inhibitor of the pathologic polymerization of antibodies into amyloid fibers.

GRP94 has a different mode of action and therefore biological activity. Although it binds peptides, its specificity is different from BiP. We use combinatorial genetic and biochemical techniques to characterize its preferred binder peptides and identify the features that it recognizes in client proteins. We developed the first cell-based assay for the chaperone function of GRP94, relying on the discovery that GRP94 is needed for production of Insulin-like growth factors, which are needed for cultured cells to cope with stress. We assay variants of GRP94 by expressing them in stressed chaperone-deficient cells. The more functional the variant chaperone, the higher the level of growth factor that is produced and the higher the survival of the cells under stress. This assay enables us to dissect the biochemical mode of action of GRP94.
Another project explores the GRP94-IGF axis in muscle physiology, using mice with targeted deletion of GRP94 in skeletal muscle. We use this model to understand what are the major client proteins of the chaperone in myocytes and to ask how modulation of GRP94 expression affect the recovery of muscle from injury.

A third project utilizes proteomic approaches to identify the interactions among ER chaperones as well as their co-factors, to understand the dynamic nature of the chaperone network and the changes in it during physiological ER stress.

Rotation Projects

1. Structure-function analysis of chaperones using cell-based assays
2. Analysis of GRP94-deficient mice
3. Proteomic analyses of chaperone-deficient cells
4. Analysis of an amyloid LC-expressing transgenic mouse
5. The GRP94-IGF axis in growth control
6. Genetic analysis of chaperone action in C. elegans

Lab personnel:
Ostrovsky, O - Research Associate
Eletto, D - Postdoctoral Fellow
Dersh, D - Graduate Student
James, J - Technician