Disease relevance of TRA1

• Using VSV8, the immunodominant peptide epitope of the vesicular stomatitis virus, and native, purified GRP94, we have investigated GRP94-peptide complex formation [1].

High impact information on TRA1

• Cells expressing a 524-base pair antisense grp78 fragment (pkASgrp78) had a diminished capacity to up-regulate grp78 and grp94 expression after ER stress [2].
• Glucose-regulated protein of 94 kDa (GRP94), the endoplasmic reticulum Hsp90, is highly homologous to cytosolic Hsp90 [3].
• In the current study, the structural and regulatory consequences of adenosine nucleotide binding to GRP94 were investigated [3].
• On the basis of these data, we propose that structural maturation of the client protein substrate, rather than ATP binding or hydrolysis, serves as the primary signal for dissociation of GRP94-client protein complexes [3].
• To identify a role(s) for ATP or ADP in the regulation of GRP94-client protein interactions, immunoglobulin (Ig) heavy chain folding intermediates containing bound GRP94 and immunoglobulin binding protein (BiP) were isolated from myeloma cells, and the effects of adenosine nucleotides on chaperone-Ig heavy chain interactions were examined [3].

Biological context of TRA1

• Structural studies of recombinant fusion protein constructs yielded identification of a 44 amino acid domain that displayed autonomous dimerization activity and conferred a highly elongated structure, characteristic of native GRP94, to the fusion protein [4].
• However, these cells were resistant to IDAM-induced apoptosis and had increased basal levels of Grp94 and a KDEL-containing protein of about 50 kDa [5].
• Current experimental evidence indicates that GRP94 functions in an as yet undefined manner in protein folding and assembly in the ER [6].
• Heterogeneity in the migration of purified GRP94 on native and denaturing PAGE was observed and demonstrated to reflect variability in the N-linked glycosylation state of the protein [6].

Anatomical context of TRA1

• Gp96/GRP94 was transiently expressed in COS-1 cells [7].
• The membrane localization of GRP94 in isolated pancreatic microsomes was assessed by alkali and detergent extraction [6].
• With this procedure, approximately 3 mg of homogeneous GRP94 can be prepared from a 25-g pancreas [6].

Associations of TRA1 with chemical compounds

• Prior heat shock did not protect cells from IDAM but pretreatment with trans-4,5-dihydroxy-1,2-dithiane (DTTox), thapsigargin, or tunicamycin enhanced expression of the endoplasmic reticulum (ER) chaperones GRP78 and GRP94 and rendered cells tolerant to IDAM [2].
• GRP94 is an abundant, resident glycoprotein of the mammalian endoplasmic reticulum lumen and member of the hsp90 family of molecular chaperones [4].
• These results are discussed with respect to a model in which peptide binding to GRP94 occurs within a hydrophobic binding pocket whose accessibility is conformationally regulated in an adenine nucleotide-independent manner [1].
• The activation of GRP94-peptide binding occurred coincident with a stable, tertiary conformational change, as identified by tryptophan fluorescence and proteolysis studies [1].

Analytical, diagnostic and therapeutic context of TRA1

• Velocity sedimentation and gel filtration chromatography were used to identify native GRP94 as a dimer with an extended, rod-like shape [4].
• Analysis of GRP94 secondary structure by circular dichroism spectroscopy indicated an identical alpha-helical content for the native, chemically denatured/renatured, and heat-shocked forms of GRP94 [1].
• These data, combined with molecular dimensions obtained from rotary shadowing electron microscopy, provide a structural model of GRP94 and identify the molecular basis of GRP94 self-assembly [4].
• Western blot revealed the induction of GRP78, GRP94, and protein disulfide isomerase at wk 3 and 4 [8].

References