Identity of the immunoglobulin heavy-chain-binding protein with the 78,000-dalton glucose-regulated protein and the role of posttranslational modifications in its binding function.

Abstract

The 78,000-dalton glucose-regulated protein (GRP78) and the immunoglobulin heavy-chain-binding protein (BiP) were shown to be the same protein by NH2-terminal sequence comparison. Immunoprecipitation of GRP78-BiP induced by glucose starvation and a temperature-sensitive mutation in a hamster fibroblast cell line demonstrated the association of GRP78-BiP with other cellular proteins. In both fibroblasts and lymphoid cells, GRP78-BiP was found to label with 32Pi and [3H]adenosine. Phosphoamino acid analysis demonstrated that GRP78-BiP is phosphorylated on serine and threonine residues. Conditions which induce increased production of GRP78-BiP resulted in decreased incorporation of 32p; and [3H]adenosine into GRP78-BiP. Furthermore, we report here that the phosphorylated form of BiP resides in the endoplasmic reticulum and that BiP which is associated with heavy chains is not phosphorylated or labeled with [3H]adenosine, whereas free BiP is. This suggests that posttranslational modifications may be important in regulating the synthesis and binding of BiP.

Enhanced synthesis of stress proteins caused by hypoxia and relation to altered cell growth and metabolism

“…However, the glucose regulated proteins are underglycosylated and migrate at a correspondingly lower molecular weight (Pouyssegur & Yamada, 1978). Further characterisation of these proteins has been accomplished by Welch et al (1983), Munro & Pelham (1986), Subjeck & Shyy (1986), Mazzarella & Green (1987), Lee (1987) and Hendershot et al (1988).…”

“…Some, at least ORPs 80 and 100, which are similar to the glucose regulated proteins, may be involved in protein processing and transport (Munro & Pelham, 1986;Mazzarella & Green, 1987;Lee, 1987;Hendershot et al, 1988). Drug resistance induced by hypoxia or glucose starvation correlates with the presence of some of these stress proteins (Shen et al, 1987;).…”

Heat Shock Proteins hsp60 and hsp70: Their Roles in Folding, Assembly and Membrane Translocation of Proteins

“…This may point to a role of the nucleotides in stabilization or induction of different conformations of BiP in the absence of ATP hydrolysis (KASSENBROCK and KELLY 1989). Furthermore, covalent modifications of hsp70 proteins, such as ADP ribosylation, methylation at lysine and arginine residues, or phosphorylation at serine and threonine residues, may be involved in the regulation of their function (WANG and LAZARIDES 1984;HENDERSHOT et al 1988). …”

“…Posttranslational modifications, including phosphorylation of serine and threonine residues and ADP ribosylation, were suggested to play a role in regulating the synthesis (HENDERSHOT et al 1988). 1988), malfolded and mutant viral glycoproteins HuRTLEYet al 1989), and hydrophilic peptides (FLYNN etal.…”

A cDNA Encoding the Endoplasmic Reticulum-Luminal Heat-Shock Protein from Spinach (Spinacia oleracea L.)

“…During normal growth the ER-luminal HSC70 is required for translocation, folding, and assembly of secretory and transmembrane proteins passing through the ER secretory pathway (Vogel et al, 1990). However, the ER-luminal HSC70s will bind to misfolded, underglycosylated, a n d mutant polypeptides, which in tum generally causes the increased expression of the HSC70 (Hendershot et al, 1988;Fontes et al, 1991). Like other HSP70s, the ER-luminal HSC70 contains a highly conserved N-terminal ATP-binding domain and shows increased ATP hydrolysis (Flynn et al, 1989) when peptides are bound at the less-conserved C-terminal peptide-binding domain.…”