Antibody News

The 78 kDa glucose-regulated protein (GRP78) is the eukaryotic orthologue to the prokaryotic heat shock 70 kDa protein 5 (HSPA5). GRP78 is also sometimes referred to as BiP. GRP78 is a member of the HSP70 family and plays dynamic roles in protein regulation within the endoplasmic reticulum. GRP78 is the most abundant chaperone in the ER and plays an important role in regulating the unfolded protein response (UPR) (1). GRP78 forms a multiprotein chaperone complex with DNAJB11, HSP90B1, HYOU, PDIA2, PDIA4, PDIA6, PPIB, SDF2L1, UGT1A1, and ERP29. It assists with protein translocation, folding, assembly, and initiation of the UPR. In an unstressed cell, GRP78 also forms a stable complex with IREI, ATF6, and PERK to keep these ER stress sensors in an inactive state. Misfolded proteins relieve the interaction of GRP78 with these proteins, freeing them to initiate the UPR. GRP78 was previously thought to be localized only to the endoplasmic reticulum; however, more recent...

Caspase-2 is a highly conserved member of the caspase family involved in the initiation and execution of apoptosis. While its function is still poorly understood, caspase-2 is thought to be important for apoptosis in response to DNA damage, bacterial infection, or abnormal mitosis (1). Caspase-2 contains an N-terminal caspase recruitment domain, the large p19 subunit containing the active site, and the small C-terminal p12 subunit (1). In response to various apoptotic signals caspase-2 undergoes dimerization. Caspase-2 then promotes its own cleavage into the mature active form consisting of a p19/p12 heterodimer (1).This active/cleaved form of caspase-2 can then cleave and activate pro-apoptotic signaling proteins such as the BCL-2 family protein BID (2). This promotes the release of cytochrome c and the induction of apoptosis (2). BID cleavage by caspase-2 was demonstrated by researchers at the University of California San Francisco (3). They...

CD63 is a type II membrane protein belonging to tetraspanin superfamily and it play key roles in the activation of several cellular signaling cascades along with acting as TIMP1 receptor. It is expressed by activated platelets, monocytes, macrophages, granulocytes, T /B cells, and different type of cancer cells. CD63 localizes to endosomes, lysosomes and on the cellular surfaces, and is often considered as a marker for late endosomes as well as for lysosomes. Besides its major role in regulation of intracellular transport and localization of several proteins, CD63 controls several processes such as cell survival, reorganization of the actin cytoskeleton, cell adhesion, spreading and migration (1). Moreover, CD63 plays an essential role during HIV-1 replication and it has been shown to incorporate into HIV-1 virions, and to colocalize with HIV-1 Env and Gag proteins in HIV-1 producing cells (2). Most of the recent studies on CD63...

Ataxia telangiectasia mutated (ATM) is essential for the maintenance of genomic stability. ATM is a 370 kDa serine-threonine kinase that is constitutively expressed in various tissues. Although primarily nuclear, ATM is also found at lower levels associated with cytoplasmic vesicles. As a PI 3-kinase family member, ATM is able to phosphorylate a wide variety of substrates including proteins involved in sensing and repairing DNA damage such as p53 and Brca1 (2). Normally ATM is found as an inactive homodimer. Following ionizing radiation ATM undergoes autophosphorylation and dissociates into catalytically active monomers. Phospho-specific ATM antibodies have aided in the identification of autophosphorylation sites and their roles in the DNA damage response (3). Examination of ATM localization by immunofluorescence using a general ATM antibody has...

Eukaryotic initiation factor 2 (eIF2) regulates global protein translation by binding to Met-tRNA and the 40S ribosome to form the pre-initiation complex. eIF2 is a heterotrimer consisting of alpha, beta, and gamma subunits. The 36kDA eIF2α subunit serves a key regulatory role. Phosphorylation of the serine residue at position 51 is able to block the formation of the pre-initiation complex and halt global protein translation. This regulatory mechanism allows cells to respond and adapt to diverse stresses such as nutrient deficiencies, viral infection, or general ER-stress. The four eIF2α kinases sense and respond to distinct types of stresses. Of these PERK (PKR-like ER kinase) phosphorylates eIF2α in response to ER-stress while GCN2 (general control non-derepressible-2) is activated in response to starvation or nutrient deficiency (1). PKR (protein kinase double-stranded RNA-dependent)...

UV resistance-associated gene (UVRAG) is a tumor suppressor that is commonly mutated in colon and breast cancer. While UVRAG was discovered for its ability to complement UV sensitivity in xeroderma pigmentosum cells, its main functions are in autophagy, endocytosis, and apoptosis. During autophagy UVRAG interacts with Beclin 1 to promote autophagosome formation. UVRAG can also interact with VPS16 to recruit membrane fusion machinery to mediate autophagosome maturation. These interactions were studied in detail in a recent study by Sun et al. (1). They used UVRAG antibody in immunoprecipitation experiments to examine the effect of Beclin 1 acetylation on UVRAG-Beclin 1 complex assembly and autophagosome maturation (1). In addition to autophagy the Beclin 1-UVRAG interaction was also shown to be essential for endocytosis and neuron viability (2). McKnight et al. used...

Transcription factor EB (TFEB) is a member of the MiTF/TFE (Microphthalmia/TFE) subfamily of basic/helix-loop-helix/leucine zipper transcription factors. This group of proteins is involved in the proliferation and development of specific cell types such as osteoclasts or melanocytes. Recently scientists have begun to uncover the roles of MiTF/TFE proteins in organelle biogenesis and energy metabolism (1). TFEB, for example, is a known regulator of lysosome biogenesis. By binding to motifs known as Coordinated Lysosomal Expression and Regulation (CLEAR) elements found within the promoters of lysosomal genes TFEB is able to activate their transcription (1). These target genes include the autophagy genes UVRAG, ATG9B, MAP1LC3B, and SQSTM1. In this manner TFEB can regulate energy metabolism by influencing the levels of lysosomes and...

WD repeat domain phosphoinositide-interacting protein 1 (WIPI) is involved in the lysosomal degradation of cytoplasmic components during starvation-induced autophagy. WIPI1 is a seven bladed beta-propeller protein that provides a scaffold for the assembly of multimeric protein complexes (1). During the assembly of the autophagosome WIPI1 interacts with the lipid phosphatidylinositol-3 phosphate (PI3P) and mediates the recruitment of the large multimeric complex of ATG12-ATG5-ATG16 (1). This complex functions as an E3 ligase during the conjugation of phosphatidylethanolamine to LC3. LC3 can then be incorporated into the expanding autophagosomal membrane and recruit substrates that have been targeted for degradation (1). These events were characterized by Polson et al. (2). Using the WIPI1 antibody for western...

Autophagy is an important cellular process involved in degradation and recycling of cellular macromolecules in response to stress or starvation. Autophagy is carried out in four main phases: phagophore nucleation, autophagosome elongation, docking and fusion with a lysosome, and vesicle breakdown and degradation. ULK1, also known as UNC51-like autophagy activating kinase 1, is a 112 kDa protein with serine-threonine kinase activity. ULK1 is one of two mammalian homologues of the yeast ATG1 kinase, known for its role in autophagy initiation (1). ULK1 forms a complex with ATG13 and FIP200 which is activated by mTORC1 and AMPK in the setting of nutrient and energy deprivation (2). Active ULK1 subsequently phosphorylates Beclin-1, which induces the autophagic activity of VPS34 complexes bound to ATG14L via PI3P. VPS34 is a mammalian class III PI3K...

Autophagy is an important cellular process that maintains homeostasis by degrading and recycling damaged proteins and organelles. Autophagy receptors, such as p62/SQSTM1, recognize these intracellular cargo and mediate their engulfment by the double-membrane autophagosome. The autophagosomes are subsequently targeted to the lysosome for degradation. An early regulatory step in this process is the activation and lipidation of ATG8 related proteins such as microtubule-associated protein-1 light chain 3 (LC3). Conjugation of LC3 to phosphatidlyethanolamine (PE) is needed to localize LC3 to the assembling autophagosome and to recruit the core autophagy machinery. This lipidation step depends on activation by the ATG4 family of proteins, also knowns as autophagins. ATG4 is a cysteine protease that cleaves and activates LC3 and LC3-related proteins at a conserved glycine residue to allow PE conjugation by the...

Phosphatidylinositol 3-kinases (PI3Ks) are a group of lipid kinases with important roles in signal transduction. PI3Ks are involved in signal propagation for diverse receptors including tyrosine kinase receptors and G-protein coupled receptors. Class I PI3Ks consist of two subunits: the regulatory p85 subunit and the catalytic p110 subunit (1). p85 binds to phosphorylated tyrosine residues found on activated tyrosine kinase receptors and mediates the translocation of the p110 subunit to the cell membrane (2). Once at the cell periphery PI3K phosphorylates the membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP2) to generate phosphatidylinositol 3,4,5-trisphosphate (PIP3). PIP3 acts as a second messenger by recruiting the kinase Akt and facilitating its activation (2). Akt can then activate downstream effectors to regulate diverse cell behaviors including growth, proliferation, and migration. PI3Ks are...

T-cells infiltrating sites of inflammation of the skin typically express the cutaneous lymphocyte-associate antigen (CLA). This antigen is defined by the binding of the monoclonal CLA antibody HECA-452. The CLA antigen is a fucose-containing oligosaccharide and is found on many of the ligands that are recognized by the adhesion proteins P-selectin and E-selectin. CLA is primarily expressed by memory T-cells. Homing of memory T-cells to sites of inflammation is mediated by the adhesion of CLA coated proteins to vascular endothelial cells expressing P-and E-selectins. Early studies of P- and E-selectin binding to glycoprotein ligands revealed the importance of CLA coating for ligand binding. Borges et al. used the HECA-452 CLA antibody to show PSGL-1 exists in two forms, one with CLA and the other without...