Antibody News

ULK1 - mammalian homologue of the yeast ATG1 kinase

Wednesday, August 26, 2015 - 15:09

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...

S6K - a serine/threonine kinase with diverse roles in cell survival and cell cycle progression

Monday, August 24, 2015 - 13:25

S6K is a serine/threonine kinase that is a member of the ribosomal S6 kinase (RSK) family. S6K exists in two main isoforms, S6K1 and S6K2, which can also be alternatively spliced to produce different splice forms. S6K1 has two major splicing products that are approximately 70 kDa and 85 kDa, known as p70S6K and p85S6K respectively. S6K is activated via phosphorylation by mTORC1 which relieves the autoinhibition of S6K. Active S6K phosphorylates the ribosomal S6 protein, which induces protein synthesis and cell growth and proliferation. S6K also phosphorylates EIF4B and EEF2K to upregulate protein synthesis. Many binding partners of S6K have been identified and indicate many roles for S6K in cellular growth, proliferation, and survival. S6K also plays a role in a negative feedback loop for mTOR signaling by phosphorylating RICTOR (1). RICTOR directly inhibits mTORC2 and AKT1 which ultimately impedes mTORC1 signaling.

Le et. al. used the...

ATG4C - A regulator of the early steps of autophagosome assembly

Friday, August 21, 2015 - 14:00

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...

VPS41 - An important regulator of lysosomal trafficking

Thursday, August 20, 2015 - 14:38

Membrane fusion is an essential step during the trafficking of endosomes and vesicles throughout the cell. Membrane fusion events are facilitated by multisubunit tethering complexes (MTC) including CORVET and HOPS. These complexes interact with Rab GTPases and SNARE proteins to promote the fusion of endosomes and lysosomes (1). In yeast VPS41 is a component of the HOPS complex that is needed for transport of endosomes and Golgi-derived vesicles to the vacuole. The choice between these two substrates is facilitated by the phosphorylation of VPS1 by Yck3 (2). Carbrera et al. used VPS41 antibodies in western blots to examine phosphorylation status of VPS41 (2). Their study identified the importance of VPS41 phosphorylation in localization and in the regulation of either endosome or vesicle targeting (2). VPS41 also seems to play a role in the transport and fusion of autophagosomes. A group from the University of British Colombia...

PI3 Kinase p110 delta - A cell-type specific lipid kinase with essential roles in leukocyte biology

Wednesday, August 19, 2015 - 14:00

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...

CHOP/GADD153 - A regulator and marker for ER-stress induced apoptosis

Monday, August 17, 2015 - 14:45

C/EBP homologous protein (CHOP) is a transcription factor that regulates apoptosis in response to cellular stress. CHOP also known as growth arrest and DNA damage 153 (GADD153) was first cloned because of its induction in response to genotoxic stress such as UV irradiation. CHOP has now been shown to be induced mainly by ER-stress (1). CHOP is normally expressed at low levels and localizes to the cytoplasm. Cellular stress triggers an upregulation of CHOP levels and accumulation in the nucleus where it can act as either a transcriptional repressor or activator (1). CHOP contains an N-terminal transcriptional activation domain and a C-terminal basic leucine zipper domain responsible for DNA binding (1). In the nucleus CHOP forms heterodimers with C/EBP family transcription factors to either enhance promoter binding or to inhibit their activity. In this manner CHOP regulates genes involved in cell survival and death (1). ER-...

CLA - guiding T-cells to sites of inflammation

Friday, August 14, 2015 - 09:05

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...

cIAP1 - An apoptotic regulator with implications in drug resistant cancers

Thursday, August 13, 2015 - 14:44

Cellular inhibitor of apoptosis protein-1 (cIAP-1) is an anti-apoptotic protein that is able to bind to caspases and inhibit their activity. Additionally cIAP-1 contains a RING domain with E3 ubiquitin ligase activity that is able to mediate the regulation of NF-kB signaling through the ubiquitination and degradation of various substrate proteins. Depending on cellular context, the RING domain of cIAP-1 can either promote or inhibit apoptosis. cIAP-1 functions in many cellular processes including inflammation, apoptosis, and the unfolded protein response making it an important player and potential target in various pathological conditions. For example, cIAP-1 levels were found to be a useful prognostic marker for the diagnosis and treatment of bladder cancer (1). Given the increased expression of cIAP-1 in cancer, small molecules targeting cIAP-1 for degradation have shown promise for sensitizing cancer cells to apoptosis (2). Depletion of IAP family proteins not only...

HIF-3 alpha: a versatile target with hypoxia dependent and independent functions

Wednesday, August 12, 2015 - 11:43

By: Subhash Gangar

HIF-3 alpha (hypoxia-inducible factor 3-alpha/ HIF3A) represents an isoform of HIF-alpha subunits which heterodimerize with stable beta subunit (HIF-beta) for the regulation of HIF target genes through binding to hypoxia response elements/HRE in the promoter regions. HIF-3 alpha is the least studied member of HIF family but it is known to be regulated by HIF1 at the transcriptional level and it exerts inhibitory effects on HIF1 alpha or HIF-dependent gene regulation, in a cell-type specific manner. HIF‑3 alpha has a transcriptional regulatory function, which negatively affects the gene expression by competing with HIF-1 alpha and HIF-2 alpha in binding to transcriptional elements of target genes during hypoxia, and its role as transcription factor has been confirmed recently with the identification of HIF-3...

ATG16L2 - An autophagy-related protein with unknown functions

Monday, August 10, 2015 - 14:48

Autophagy is a process by which cells degrade and recycle damaged organelles or misfolded proteins. These various cargo are engulfed in a double-membrane structure called the autophagosome. The autophagosome then fuses with the lysosome to facilitate the degradation of the cargo. This process requires the concerted effort of an extensive network of proteins. One of the early steps of autophagosome assembly is the formation of the large multimeric ATG12-ATG5-ATG16 complex. This complex acts as an E3 ligase during the lipidation of ATG8. ATG8 is then incorporated into the expanding autophagosomal membrane and facilitates the recruitment of core autophagy machinery and substrates targeted for degradation. ATG16L2 is an isoform of ATG16 whose function is still unclear. While the isoform ATG16L1 is essential for autophagy, ATG16L2 does not seem to be important (1). In an examination of ATG16L2...

ATG4D - A regulator of autophagy and apoptosis

Friday, August 7, 2015 - 13:15

Autophagy is an essential cellular process whereby damaged proteins and organelles are degraded and recycled. Autophagy, while happening constantly at a basal level, is tightly regulated and can be further induced under cellular stress. One of the regulators of the early steps of autophagy is ATG4. The ATG4 family of cysteine proteases consists of 4 homologs: ATG4A, ATG4B, ATG4C, and ATG4D. This family of proteins regulates the initiation of autophagosome assembly by cleaving ATG8-like proteins, including LC3, at a conserved glycine residue and thereby activating it. Cleaved LC3 can then be lipidated by the ATG12-ATG5-ATG16 protein complex. LC3 conjugated to the lipid PE is inserted into the assembling autophagosome membrane where it recruits the core...

HSP90 - an essential eukaryotic protein with implications for drug development

Thursday, August 6, 2015 - 14:27

The heat-shock protein 90 (HSP90) family is a group of highly conserved molecular chaperones with important functions in protein folding and in signal transduction. The HSP90 protein structure is so well conserved that some HSP90 antibodies are reactive with a broad range of species from humans to chickens (1). In humans there are 17 known genes encoding the HSP90 family members. The HSP90 family consists of 4 different classes: HSP90AA, HSP90AB, HSP90B, and TRAP. These classes are defined by their diversity of functions and sub cellular localization. HSP90 isoforms are known to localize to the cytosol, nucleoplasm, endoplasmic reticulum, mitochondria, and chloroplasts. HSP90 is an abundant protein that maintains cellular homeostasis by promoting the proper folding of hundreds of substrate proteins referred to as clients. These clients range from protein kinases to transcription factors making HSP90 an essential component of many...

Hsp70/Hsc70 - A chaperone for protein folding and autophagy

Wednesday, August 5, 2015 - 15:19

The heat shock protein 70 (Hsp70) family are a group of chaperones involved in various cellular processes including protein folding and protein degradation. In addition to maintaining normal cellular homeostasis by processing newly synthesized protein, the Hsp70 family is also important in controlling intracellular signaling pathways by regulating the folding and activity of signaling proteins. The various groups within the Hsp70 family are characterized by their expression levels, activities, and subcellular localization (1). For example, the heat shock cognate 70 (Hsc70) group is defined by its constitutive expression and cytoplasmic localization. The Hsp70 group on the other hand is induced by cellular stress such as temperature changes or exposure to toxic chemicals. BiP, another Hsp70 family member, localizes to the ER and acts as a chaperone for secreted or membrane proteins (1). Hsp70 family members contain two domains: the N-...

FLT3 - receptor tyrosine kinase with a role in acute myeloid leukemia

Monday, August 3, 2015 - 14:37

Fms-like tyrosine kinase-3 (FLT3) is a Type III receptor tyrosine kinase expressed by hematopoietic progenitor cells. FLT3 is also sometimes referred to as FLK2 or CD135. The FLT3 protein exists in two states- membrane bound (160 kDa) and cytoplasmic (140 kDa) (1). The FLT3 ligand induces autophosphorylation of FLT3 which allows binding of scaffold and effector molecules. Activated FLT3 is capable of phosphorylating and activating PI3K, PLC-γ, Shc, Grb2, and Src (2). FLT3 signaling ultimately activates the AKT and MAPK pathways to promote cell growth and survival. Mutations in FLT3 account for nearly one third of acute myeloid leukemia (AML) cases. The most common FLT3 derangement in AML is an internal tandem duplication (ITD) in the juxtamembrane domain. FLT3-ITD causes constituent activation of FLT3 signaling. Other activating mutations have also been identified, suggesting an important role for FLT3 in leukemogenesis. FLT3 overexpression correlates with a poor...

CD98 - cell surface glycoprotein that promotes cell adhesion, growth, and survival

Friday, July 31, 2015 - 13:24

CD98 is a heterodimeric glycoprotein that contains an 80 kDa heavy chain and a 40 kDa light chain. The CD98 heavy chain is also known as the 4F2 antigen heavy chain or FRP-1, and it is encoded by the SLC3A2 gene. The CD98 heavy chain is capable of binding to β-integrins to mediate cell adhesion, motility, growth, and survival (1). Meanwhile, the CD98 light chain allows amino acid transport. Different isoforms of the light chain allow expression of six different L-amino acid transporters. The CD98 heavy chain can be expressed independently; however, expression of the CD98 light chain is dependent on the presence of the heavy chain. CD98 was first identified for its role in lymphocyte activation and the adaptive immune response (2). In adaptive immunity, antigens are presented to a pool of lymphocytes until its complementary match is identified. Upon matching, clonal expansion of the lymphocyte is crucial for combating the infection and...

Akt1 - a central player in cell survival signaling

Thursday, July 30, 2015 - 13:17

Akt1 is one of three isoforms of Akt belonging to the AGC family of serine/threonine kinases (Akt1, Akt2, and Akt3). All Akt isoforms contain an N-terminal Plekstrin Homology (PH) domain, a C-terminal regulatory domain, and a central catalytic kinase domain (1). Akt is a major downstream target of the PI3-K signaling pathway. The Akt1 isoform is fully activated by phosphorylation at three sites- T308, T450, and S473. Akt1 resides in an inactive state due to intramolecular interactions between the PH domain and the kinase domain. PI3-K signaling induces a conformational change that exposes the active sites to allow phosphorylation and activation of Akt1 (1). Akt plays a variety of roles in normal cellular metabolism, growth, proliferation, and survival. It has also been implicated in malignancies as a driver of angiogenesis, migration, and invasion. Recent studies have begun to tease apart the signaling specificity of the three Akt isoforms. Akt1 is expressed in many...

Caspase-4 - a human protease with roles in inflammation and immunity

Wednesday, July 29, 2015 - 15:28

Caspases are a family of cysteine-aspartic acid proteases that cleave caspase proenzymes as well as other protein substrates. Caspases are well known for their role in apoptosis, but they also play a significant role in other cellular processes including inflammation (1). Apoptotic caspases include Caspases-3, -6, -7, -8, and -9. Meanwhile, human inflammatory caspases include Caspases-1, -4, -5, and -12. The role of Caspase-4 and -5 have been particularly difficult to study given that mice only express inflammatory Caspases-1,-11, and -12. Recent data suggests that human caspases-4 and -5 are orthologs of the murine Caspase-11 (1). Full length Caspase-4 is a 45 kDa protein while the cleaved isoform is only...

TSC2 - GTPase activating protein involved in cell cycle inhibition

Monday, July 27, 2015 - 14:59

TSC2 is a tumor suppressor gene that encodes a 200 kDa protein called tuberin. TSC2 heterodimerizes with TSC1 to form a complex with GTPase-activating protein (GAP) activity. The C-terminus of TSC2 contains the GAP domain responsible for this catalytic activity. The complex was first discovered through its role in the tumor-forming condition Tuberous Sclerosis. Mutations in TSC1 and TSC2 can either destabilize the complex or compromise the GAP activity. The TSC1-TSC2 complex acts as a GAP for the small G-protein Rheb, expressed ubiquitously throughout the body (1). Rheb inhibits mTOR signaling to downregulate protein synthesis and cell growth. Thus in the absence of TSC1-TSC2, mTOR signaling allows unchecked cellular growth and proliferation. TSC1-TSC2 acts as a nutrient sensor for amino acids, growth factors, hormones, etc. and mediates cell cycle progression. The TSC1-TSC2 complex can be phosphorylated at a number of sites that are either activating or inactivating....

ATG4B - a cysteine protease involved in autophagosome elongation

Friday, July 24, 2015 - 11:29

Autophagy can be broken down into 4 main stages: phagophore nucleation, autophagosome elongation, autophagosome docking and fusion with a lysosome, and vesicle breakdown and degradation. ATG4B is one of four ATG4 homologs (ATG4A, ATG4B, ATG4C, and ATG4D) involved in autophagosome elongation. ATG4B encodes a 48 kDa protein called autophagin-1 that is a member of the C54 family of cysteine proteases. ATG4B exists in an autoinhibited state where two of its structural domains hide its catalytic cysteine (1). ATG4B binding to its substrate induces a conformational change that exposes the active site and allows cleavage of the substrate. ATG4B is the least specific of the ATG4 family and is capable of recognizing multiple homologs of its substrate ATG8 (2).

ATG8 is an ubiquitin-like protein involved in...

TSC1 - a negative regulator of mTOR signaling

Thursday, July 23, 2015 - 14:57

TSC1 is a tumor suppressor gene that encodes a 130 kDa protein called hamartin. TSC1 was first identified as an oncogenic driver of Tuberous Sclerosis, a condition characterized by numerous benign tumors of the skin, brain, heart, and lungs. A mutation in TSC1 is responsible for the uncontrolled growth characteristic of these tumors. This discovery led to a greater understanding of the physiologic role of TSC1 as a negative cell cycle regulator. The distinct but related gene TSC2 encodes a 200 kDa protein called tuberin. TSC1 and TSC2 heterodimerize to form a complex that acts as a GTPase-activating protein (GAP) for the G-protein Rheb (1). Rheb is a member of the Ras family that inhibits mTORC1 signaling when activated by the TSC1-TSC2 complex. mTORC1 signaling promotes cell growth and proliferation and aberrant signaling promotes tumor formation. The TSC1-TSC2 complex acts as a sensor for levels of growth factors, amino acids, and other...

ATG16L1 - a key player in the development of the autophagosome

Wednesday, July 22, 2015 - 13:37
Untitled Document

Like apoptosis, autophagy is a highly regulated physiologic process that involves cellular degradation and recycling of organelles and macromolecules. Autophagy is a survival mechanism induced by states of stress, starvation, and infection. A double membraned autophagosome sequesters the desired cellular components before fusing with a lysosome to form an autolysosome destined for degradation. LC3 lipidation and recruitment to the autophagosome is crucial to its maturation and eventual fusion with a lysosome. ATG16L1 (autophagy-related protein 16-1) forms a highly conserved complex with ATG5 and ATG12 to direct LC3 to the autophagosome (1). ATG16L1 is a 68 kDa protein that exists in the cytoplasm and is directed to the preautophagosomal structure (PAS) as needed. ...

OATP8 - A membrane transport protein responsible for cancer drug uptake

Monday, July 20, 2015 - 14:21

Human hepatocytes express important transport proteins that are responsible for the uptake and removal of organic anions from the blood. These proteins are members of the organic anion-transporting polypeptide (OATP) family and are essential for proper liver function. OATPs are encoded by the SLC21 gene family and contain 12 transmembrane alpha-helices and are primarily expressed in the liver. The OATP family transports endogenous substrates like bile salts and steroid hormones as well as exogenous molecules like anticancer drugs and imaging agents. This broad specificity makes OATPs an important research topic for understanding basic liver biology and for designing therapeutic and diagnostic strategies. Of particular importance is OATP8. Early studies of OATP8 used immunofluorescent staining with OATP8 antibodies to demonstrate basolateral localization in human hepatocytes (1). Additionally immunoblotting with...

Thrombomodulin - A multifunctional protein with roles in inflammation and coagulation

Friday, July 17, 2015 - 14:40

Thrombomodulin, also known as BDCA-3, is a glycosylated transmembrane protein present on the surface of vascular endothelial cells. Thrombomodulin is a high-affinity receptor for thrombin, a key protein in the coagulation cascade. Formation of the thrombomodulin-thrombin complex blocks the thrombin dependent conversion of fibrinogen to fibrin and also catalyzes the activation of protein C. Active protein C is able to proteolytically inactivate enhancers of the coagulation cascade. Thrombomodulin’s dual ability to directly block thrombin function and to activate a negative regulator of coagulation makes it essential component of the anticoagulation system. Thrombomodulin is known for its role in anticoagulation but has recently been shown to have important functions in inflammation as well. The extracellular N-terminus of thrombomodulin consists of two domains; a lectin-like domain and an EGF-repeat domain. The EGF-repeat domain is responsible for thrombin binding...

5 Simple Western Antibody Facts

Thursday, July 16, 2015 - 12:46

Novus Biologicals has 800+ antibodies and 650 unique targets validated on the Simple Western platform. All are certified in-house by our experienced scientists. They are backed by 175+ peer reviews and more than 5,600 citations in a variety of applications. Learn more about Simple Western in the Infographic below and check out our list of certified antibodies

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Beclin 2, a mammal-specific homolog of Beclin 1 with unique functional similarities and differences

Wednesday, July 15, 2015 - 15:57
Beclin 2 (BECN2) is also called Beclin-1-like protein 1/ BECN1P1 and it was recently identified by He et al 2013 as a mammal-specific homolog of the evolutionarily conserved protein Beclin 1 which is well established for its role in the regulation of autophagy and oncogenic suppression (1). He et al 2013 documented that human Beclin 2 is 57% similar to Beclin 1, and they confirmed its presence in several tissues including brain, placenta, thymus, uterus and skeletal muscles. Further studies from various labs established Beclin-2’s critical role in two distinct lysosomal degradation pathways: as a regulator of autophagy and as a regulator of G-protein coupled receptors/GPCRs turnover. Like Beclin 1, Beclin 2 was also found to regulate autophagy and its effects were demonstrated in basal or starvation-induced autophagy experiments involving bafilomycin A1 and cultured mammalian cells wherein it...

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