The ER Stress-induced Antibody Sampler Kit contains reagents to investigate ER stress-induced signaling within the cell. The kit contains enough primary antibodies to perform four western blot experiments per primary antibody.
Specificity / Sensitivity
Each antibody in the ER Stress-induced Antibody Sampler Kit detects endogenous levels of its target protein. Phospho-eIF2α (Ser51) (D9G8) XP® Rabbit mAb detects endogenous eIF2α only when phosphorylated at Ser51. The antibody does not recognize elF2α phosphorylated at other sites. Phospho-SAPK/JNK (Thr183/Tyr185) (81E11) Rabbit mAb detects endogenous levels of p46 and p54 SAPK/JNK only when phosphorylated at Thr183 and Tyr185. This antibody may cross-react with phosphorylated p44/42 or p38 MAP kinases. JNK1 (2C6) Mouse mAb detects endogenous levels of total JNK1 protein. This antibody may cross react with recombinant levels JNK2 protein. The antibody does not cross react with JNK3 protein.
Source / Purification
Monoclonal antibody is produced by immunizing animals with a synthetic peptide corresponding to residues surrounding Gly584 of human BiP, residues surrounding Ser36 of human Atg12 protein, residues surrounding Thr72 of human Beclin-1, residues surrounding Ser51 of human eIF2α, residues surrounding Thr183/Tyr185 of human SAPK/JNK, residues of a purified recombinant human eIF2α, and residues corresponding to the amino terminus of human JNK1.
The endoplasmic reticulum (ER) is an organelle with essential biosynthetic and signaling functions in eukaryotic cells (1). Post synthesis of secretory and transmembrane proteins on polysomes, proteins are translocated into the ER where they are often modified by disulfide bond formation, amino-linked glycosylation, and folding. Different physiological and pathological conditions can disturb proper protein folding in the ER causing ER stress (1). ER stress activates an intracellular signaling transduction pathway called unfolded protein response (UPR) and autophagy to avoid cell death (2). The main role of UPR is to improve the protein load on the ER by shutting down protein translation and gene transcription to enhance ER's folding capacity (2). On the other hand, autophagy is a catabolic process for the autophagosomic-lysosomal degradation of bulk cytoplasmc contents (3,4). One of the chaperones aiding in proper protein folding is Binding immunoglobulin Protein (BiP) (5,6). BiP works by binding to misfolded proteins to prevent them from forming aggregates and assists in proper refolding (7). The molecular machinery of autophagy was largely discovered in yeast and referred to as autophagy-related (Atg) genes. Formation of the autophagosome involves a ubiquitin-like conjugation system in which Atg12 is covalently bound to Atg5 and targeted to autophagosome vesicles (8-10). One of the proteins critical to autophagy process is Beclin-1, the mammalian orthologue of the yeast autophagy protein Apg6/Vps30 (11). Beclin-1 can complement defects in yeast autophagy caused by loss of Apg6 and can also stimulate autophagy when overexpressed in mammalian cells (12). Mammalian Beclin-1 was originally isolated in a yeast two-hybrid screen for Bcl-2 interacting proteins and has been shown to interact with Bcl-2 and Bcl-xL, but not with Bax or Bak (13). Phosphorylation of the eukaryotic initiation factor 2 (eIF2) α subunit is a well-documented mechanism to downregulate protein synthesis under a variety of stress conditions. eIF2 binds GTP and Met-tRNAi and transfers Met-tRNA to the 40S subunit to form the 43S preinitiation complex (14,15). Kinases that are activated by viral infection (PKR) can phosphorylate the α subunit of eIF2 (16,17). Induction of PKR by IFN-γ and TNF-α induces potent phosphorylation of eIF2α at Ser51 (18,19). There are three SAPK/JNK genes each of which undergoes alternative splicing, resulting in numerous isoforms (20). The IRE1, a transmembrane serine/threonine kinase (21,22), through its kinase activity activates SAPK/JNK in the early stage of ER stress in order to induce autophagosome formation (23).