GRP78 is a ubiquitously expressed, 78-kDa glucose regulated protein, and is commonly referred to as an
immunoglobin chain binding protein (BiP). The BiP
proteins are categorized as stress response proteins
because they play an important role in the proper folding
and assembly of nascent protein and in the scavenging of
misfolded proteins in the endoplasmic reticulum lumen.
Translation of BiP is directed by an internal ribosomal
entry site (IRES) in the 5' non-translated region of the BiP
mRNA. BiP IRES activity increases when cells are heat
stressed (1).
GRP78 is also critical for maintenance of cell homeostasis
and the prevention of apoptosis (2). Luo et al. have
provided findings that suggest GRP78 is essential for
embryonic cell growth and pluripotent cell survival (3).
In terms of diseases, GRP78 has been shown to be a reliable
biomarker of hypoglycemia, to serve a neuroprotective
function in neurons exposed to glutamate and oxidative stress
(4), and its protein levels are reduced in the brains of
Alzheimer’s patients (5). Also, the induction of the GRP78
protein that results in severe glucose and oxygen deprivation
could possible lead to drug resistance to anti-tumor drugs (6,
7).