Fibroblast growth factor-1 interacts with the glucose-regulated protein GRP75/mortalin

Abstract

Fibroblast growth factor-1 (FGF-1), which lacks a signal peptide and is intracellularly localized as a result of endogenous expression or endocytosis, is thought to be involved in regulating cell growth and differentiation. In the study reported here, we purified proteins that bind intracellular FGF-1. Affinity adsorption was used to purify FGF-1-binding proteins from rat L6 cells expressing FGF-1. One of the isolated proteins was identified as the glucose-regulated protein GRP75/mortalin/PBP-74/mthsp70, a member of the hsp70 family of heat-shock proteins known to be involved in regulating glucose responses, antigen processing and cell mortality. The interaction of FGF-1 and GRP75/mortalin in vivo was confirmed by co-immunoprecipitation, immunohistochemical co-localization in Rat-1 fibroblasts and by using the yeast two-hybrid system. Moreover, a binding assay in vitro with the use of recombinant FGF-1 and mortalin demonstrated a direct physical interaction between the two proteins. These results reveal that GRP75/mortalin is an intracellular FGF-1-binding protein in cells and suggest that GRP75/mortalin is involved in the trafficking of and/or signalling by FGF-1.

Sarcolipin retention in the endoplasmic reticulum depends on its C-terminal RSYQY sequence and its interaction with sarco(endo)plasmic Ca 2 +-ATPases

“…Interestingly, GRP75 has many assigned functions, including intracellular trafficking (26,27). Although the identification of this protein as an NF-SLN-interacting candidate appeared particularly attractive to investigate further, we were unable to verify these findings by conventional IPs.…”

Magnetic nanoparticle-based isolation of endocytic vesicles reveals a role of the heat shock protein GRP75 in macromolecular delivery

“…Previous studies have suggested that GRP75 (also known as "PBP74") not only is present in the endoplasmic reticulum (ER) but also is associated with the plasma membrane and in early endocytic vesicles in immune cells, suggesting a role in antigen processing (14). Others have reported on cytosolic localization of GRP75 (also known as "mortalin"), where it may regulate the activity of p53 (15) and FGF (16). More recent proteomic analyses of detergent-resistant membrane fractions have suggested GRP75 is a ubiquitously expressed membrane lipid raft protein (17); however, the role of GRP75 in endocytic mechanisms remains unknown.…”

Cytokine- or chemically derived nitric oxide alters the expression of proteins detected by two-dimensional gel electrophoresis in neonatal rat islets of Langerhans.

“…It is of interest that a third protein in the large heatshock family, mortalin (GRP75, match number 330 and 340) (68), seems to be posttranslationally modified in response to cytokines and the NO inhibitor because the expression levels were changed in opposite directions in the two spots. GRP75 is a glucose-regulated stress-inducible mitochondrial chaperone protein, possibly involved in antigen-processing and cell mortality (68).…”