Background: Activation of protein kinase C (PKC) is one of the earliest events in a cascade that controls a variety of cellular responses, including secretion, gene expression, proliferation, and muscle contraction (1,2). PKC isoforms belong to three groups based on calcium dependency and activators. Classical PKCs are calcium-dependent via their C2 domains and are activated by phosphatidylserine (PS), diacylglycerol (DAG), and phorbol esters (TPA, PMA) through their cysteine-rich C1 domains. Both novel and atypical PKCs are calcium-independent, but only novel PKCs are activated by PS, DAG, and phorbol esters (3-5). Members of these three PKC groups contain a pseudo-substrate or autoinhibitory domain that binds to substrate-binding sites in the catalytic domain to prevent activation in the absence of cofactors or activators. Control of PKC activity is regulated through three distinct phosphorylation events. Phosphorylation occurs in vivo at Thr500 in the activation loop, at Thr641 through autophosphorylation, and at the carboxy-terminal hydrophobic site Ser660 (2). Atypical PKC isoforms lack hydrophobic region phosphorylation, which correlates with the presence of glutamic acid rather than the serine or threonine residues found in more typical PKC isoforms. The enzyme PDK1 or a close relative is responsible for PKC activation. A recent addition to the PKC superfamily is PKCμ (PKD), which is regulated by DAG and TPA through its C1 domain. PKD is distinguished by the presence of a PH domain and by its unique substrate recognition and Golgi localization (6). PKC-related kinases (PRK) lack the C1 domain and do not respond to DAG or phorbol esters. Phosphatidylinositol lipids activate PRKs, and small Rho-family GTPases bind to the homology region 1 (HR1) to regulate PRK kinase activity (7).
Background: The p53 tumor suppressor protein plays a major role in cellular response to DNA damage and other genomic aberrations. Activation of p53 can lead to either cell cycle arrest and DNA repair or apoptosis (1). p53 is phosphorylated at multiple sites in vivo and by several different protein kinases in vitro (2,3). DNA damage induces phosphorylation of p53 at Ser15 and Ser20 and leads to a reduced interaction between p53 and its negative regulator, the oncoprotein MDM2 (4). MDM2 inhibits p53 accumulation by targeting it for ubiquitination and proteasomal degradation (5,6). p53 can be phosphorylated by ATM, ATR, and DNA-PK at Ser15 and Ser37. Phosphorylation impairs the ability of MDM2 to bind p53, promoting both the accumulation and activation of p53 in response to DNA damage (4,7). Chk2 and Chk1 can phosphorylate p53 at Ser20, enhancing its tetramerization, stability, and activity (8,9). p53 is phosphorylated at Ser392 in vivo (10,11) and by CAK in vitro (11). Phosphorylation of p53 at Ser392 is increased in human tumors (12) and has been reported to influence the growth suppressor function, DNA binding, and transcriptional activation of p53 (10,13,14). p53 is phosphorylated at Ser6 and Ser9 by CK1δ and CK1ε both in vitro and in vivo (13,15). Phosphorylation of p53 at Ser46 regulates the ability of p53 to induce apoptosis (16). Acetylation of p53 is mediated by p300 and CBP acetyltransferases. Inhibition of deacetylation suppressing MDM2 from recruiting HDAC1 complex by p19 (ARF) stabilizes p53. Acetylation appears to play a positive role in the accumulation of p53 protein in stress response (17). Following DNA damage, human p53 becomes acetylated at Lys382 (Lys379 in mouse) in vivo to enhance p53-DNA binding (18). Deacetylation of p53 occurs through interaction with the SIRT1 protein, a deacetylase that may be involved in cellular aging and the DNA damage response (19).
Background: Key steps in translational control occur at the level of eukaryotic initiation factor 4F (eIF4F) and p70 S6 kinase regulation. eIF4F is a complex whose functions include the recognition of the mRNA 5' cap structure. Several stimuli, such as insulin and various growth and survival factors, regulate the eIF4F complex and p70 S6 kinase primarily by triggering a signaling cascade dependent on sequential activation of PI3K, Akt/PKB and mTOR/FRAP kinases. Akt is activated by phosphorylation within the C-terminus at Ser473 and within the activation loop at Thr308 by phospholipid-dependent kinases. Inactivation in vivo of PI3K by the highly selective inhibitor LY294002 inhibits Akt and downstream elements of this cascade. Direct phosphorylation of mTOR/FRAP at Ser2448 by Akt is a key regulatory event controlling its kinase activity. mTOR/FRAP activity can be effectively blocked by Rapamycin, leading to inactivation of eukaryotic initiation factor 4E binding protein 1 (4E-BP1), an inhibitor of translation initiation, and activation of p70 S6 kinases. Inactivation of 4E-BP1 by sequential phosphorylation causes the release of eIF4E, which, together with eIF4G and other factors, forms a functional eIF4F cap binding complex. p70 S6 kinases phosphorylates the 40S ribosomal subunit protein S6 and stimulates the translation of 5' oligopyrimidine tract containing mRNAs. The Erk pathway is also involved in regulation at this level by regulating the eIF4E kinase, Mnk1, and activating p70 S6 kinase. Tuberin, a product of the tumor supressor gene TSG2, is directly phosphorylated atThr1462 by Akt/PKB. Tuberin inhibits the mammalian target of rapamycin, mTOR, which results in inhibition of p70 S6 kinase and activation of 4E-BP1 and, therefore, inhibition of translation.
Background: The cell division cycle demands accuracy to avoid the accumulation of genetic damage. This process is controlled by molecular circuits called "checkpoints" that are common to all eukaryotic cells (1). Checkpoints monitor DNA integrity and cell growth prior to replication and division at the G1/S and G2/M transitions, respectively. The cdc2-cyclin B kinase is pivotal in regulating the G2/M transition (2,3). Cdc2 is phosphorylated at Thr14 and Tyr15 during G2-phase by the kinases Wee1 and Myt1, rendering it inactive. The tumor suppressor protein retinoblastoma (Rb) controls progression through the late G1 restriction point (R) and is a major regulator of the G1/S transition (4). During early and mid G1-phase, Rb binds to and represses the transcription factor E2F (5). The phosphorylation of Rb late in G1-phase by CDKs induces Rb to dissociate from E2F, permitting the transcription of S-phase-promoting genes. In vitro, Rb can be phosphorylated at multiple sites by cdc2, cdk2, and cdk4/6 (6-8). DNA damage triggers both the G2/M and the G1/S checkpoints. DNA damage activates the DNA-PK/ATM/ATR kinases, which phosphorylate Chk at Ser345 (9), Chk2 at Thr68 (10) and p53 (11). The Chk kinases inactivate cdc25 via phosphorylation at Ser216, blocking the activation of cdc2.
Background: Akt, also referred to as PKB or Rac, plays a critical role in controlling survival and apoptosis (1-3). This protein kinase is activated by insulin and various growth and survival factors to function in a wortmannin-sensitive pathway involving PI3 kinase (2,3). Akt is activated by phospholipid binding and activation loop phosphorylation at Thr308 by PDK1 (4) and by phosphorylation within the carboxy terminus at Ser473. The previously elusive PDK2 responsible for phosphorylation of Akt at Ser473 has been identified as mammalian target of rapamycin (mTOR) in a rapamycin-insensitive complex with rictor and Sin1 (5,6). Akt promotes cell survival by inhibiting apoptosis through phosphorylation and inactivation of several targets, including Bad (7), forkhead transcription factors (8), c-Raf (9), and caspase-9. PTEN phosphatase is a major negative regulator of the PI3 kinase/Akt signaling pathway (10). LY294002 is a specific PI3 kinase inhibitor (11). Another essential Akt function is the regulation of glycogen synthesis through phosphorylation and inactivation of GSK-3α and β (12,13). Akt may also play a role in insulin stimulation of glucose transport (12). In addition to its role in survival and glycogen synthesis, Akt is involved in cell cycle regulation by preventing GSK-3β-mediated phosphorylation and degradation of cyclin D1 (14) and by negatively regulating the cyclin dependent kinase inhibitors p27 Kip1 (15) and p21 Waf1/Cip1 (16). Akt also plays a critical role in cell growth by directly phosphorylating mTOR in a rapamycin-sensitive complex containing raptor (17). More importantly, Akt phosphorylates and inactivates tuberin (TSC2), an inhibitor of mTOR within the mTOR-raptor complex (18,19).
Background: Apoptosis is a regulated physiological process leading to cell death. Caspases, a family of cysteine acid proteases, are central regulators of apoptosis. Initiator caspases (including 8, 9, 10 and 12) are closely coupled to proapoptotic signals. Once activated, these caspases cleave and activate downstream effector caspases (including 3, 6 and 7), which in turn cleave cytoskeletal and nuclear proteins like PARP, α-fodrin, DFF and lamin A, and induce apoptosis. Cytochrome c released from mitochondria is coupled to the activation of caspase-9, a key initiator caspase (1). Proapoptotic stimuli include the FasL, TNF-α, DNA damage and ER stress. Fas and TNFR activate caspases 8 and 10 (2), DNA damage leads to the activation of caspase-9 and ER stress leads to the calcium-mediated activation of caspase-12 (3). The inhibitor of apoptosis protein (IAP) family includes XIAP and survivin and functions by binding and inhibiting several caspases (4,5). Smac/Diablo, a mitochondrial protein, is released into the cytosol upon mitochondrial stress and competes with caspases for binding of IAPs. The interaction of Smac/Diablo with IAPs relieves the inhibitory effects of the IAPs on caspases (6).
Background: Jaks (Janus Kinases) and Stats (Signal Transducers and Activators of Transcription) are utilized by receptors for a wide variety of ligands including cytokines, hormones, growth factors and neurotransmitters. Jaks, activated via autophosphorylation following ligand-induced receptor aggregation, phosphorylate tyrosine residues on associated receptors, Stat molecules and other downstream signaling proteins (1,2). The phosphorylation of Stat proteins at conserved tyrosine residues activates SH2-mediated dimerization followed rapidly by nuclear translocation. Stat dimers bind to IRE (interferon response element) and GAS (gamma interferon-activated sequence) DNA elements, resulting in the transcriptional regulation of downstream genes (1,2). The remarkable range and specificity of responses regulated by the Stats is determined in part by the tissue-specific expression of different cytokine receptors, Jaks and Stats (2,3), and by the combinatorial coupling of various Stat members to different receptors. Serine phosphorylation in the carboxy-terminal transcriptional activation domain has been shown to regulate the function of Stat1, -2, -3, -4 and -5 (1). Phosphorylation of Stat3 at Ser727 via MAPK or mTOR pathways is required for optimal transcriptional activation in response to growth factors and cytokines including IFN-gamma and CNTF (4,5). Jak/Stat pathways also play important roles in oncogenesis, tumor progression, angiogenesis, cell motility, immune responses and stem cell differentiation (6-11).
Background: p38 MAP kinase (MAPK), also called RK (1) or CSBP (2), is the mammalian orthologue of the yeast HOG kinase that participates in a signaling cascade controlling cellular responses to cytokines and stress (1-4). Four isoforms of p38 MAPK, p38α, β, γ (also known as Erk6 or SAPK3), and δ (also known as SAPK4) have been identified. Similar to the SAPK/JNK pathway, p38 MAPK is activated by a variety of cellular stresses including osmotic shock, inflammatory cytokines, lipopolysaccharide (LPS), UV light, and growth factors (1-5). MKK3, MKK6, and SEK activate p38 MAPK by phosphorylation at Thr180 and Tyr182. Activated p38 MAPK has been shown to phosphorylate and activate MAPKAP kinase 2 (3) and to phosphorylate the transcription factors ATF-2 (5), Max (6), and MEF2 (5-8). SB203580 (4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)-imidazole) is a selective inhibitor of p38 MAPK. This compound inhibits the activation of MAPKAPK-2 by p38 MAPK and subsequent phosphorylation of HSP27 (9). SB203580 inhibits p38 MAPK catalytic activity by binding to the ATP-binding pocket, but does not inhibit phosphorylation of p38 MAPK by upstream kinases (10).
Background: The stress-activated protein kinase/Jun-amino-terminal kinase SAPK/JNK is potently and preferentially activated by a variety of environmental stresses including UV and gamma radiation, ceramides, inflammatory cytokines, and in some instances, growth factors and GPCR agonists (1-6). As with the other MAPKs, the core signaling unit is composed of a MAPKKK, typically MEKK1-MEKK4, or by one of the mixed lineage kinases (MLKs), which phosphorylate and activate MKK4/7. Upon activation, MKKs phosphorylate and activate the SAPK/JNK kinase (2). Stress signals are delivered to this cascade by small GTPases of the Rho family (Rac, Rho, cdc42) (3). Both Rac1 and cdc42 mediate the stimulation of MEKKs and MLKs (3). Alternatively, MKK4/7 can be activated in a GTPase-independent mechanism via stimulation of a germinal center kinase (GCK) family member (4). There are three SAPK/JNK genes each of which undergoes alternative splicing, resulting in numerous isoforms (3). SAPK/JNK, when active as a dimer, can translocate to the nucleus and regulate transcription through its effects on c-Jun, ATF-2, and other transcription factors (3,5).
Background: Mitogen-activated protein kinases (MAPKs) are a widely conserved family of serine/threonine protein kinases involved in many cellular programs, such as cell proliferation, differentiation, motility, and death. The p44/42 MAPK (Erk1/2) signaling pathway can be activated in response to a diverse range of extracellular stimuli including mitogens, growth factors, and cytokines (1-3), and research investigators consider it an important target in the diagnosis and treatment of cancer (4). Upon stimulation, a sequential three-part protein kinase cascade is initiated, consisting of a MAP kinase kinase kinase (MAPKKK or MAP3K), a MAP kinase kinase (MAPKK or MAP2K), and a MAP kinase (MAPK). Multiple p44/42 MAP3Ks have been identified, including members of the Raf family, as well as Mos and Tpl2/COT. MEK1 and MEK2 are the primary MAPKKs in this pathway (5,6). MEK1 and MEK2 activate p44 and p42 through phosphorylation of activation loop residues Thr202/Tyr204 and Thr185/Tyr187, respectively. Several downstream targets of p44/42 have been identified, including p90RSK (7) and the transcription factor Elk-1 (8,9). p44/42 are negatively regulated by a family of dual-specificity (Thr/Tyr) MAPK phosphatases, known as DUSPs or MKPs (10), along with MEK inhibitors, such as U0126 and PD98059.
Background: p44/42 MAPK (Erk1/2), SAPK/JNK, and p38 MAPK function in protein kinase cascades that play a critical role in the regulation of cell growth, differentiation, and control of cellular responses to cytokines and stress. p44/42 MAPK is activated by growth and neurotrophic factors. Activation occurs through phosphorylation of threonine and tyrosine residues (Thr202 and Tyr204 in human Erk1) at the sequence T*EY* by a single upstream MAP kinase kinase (MEK). SAPK/JNK and p38 MAPK are activated by inflammatory cytokines and by a wide variety of cellular stresses. Activation of SAPK/JNK occurs via phosphorylation at Thr183 and Tyr185 by the dual specificity enzyme SEK/MKK4. Both MKK3 and SEK phosphorylate p38 MAPK on tyrosine and threonine at the sequence T*GY* to activate p38 MAP kinase (1-5).
Background: Rapamycin is a bacterial macrolide with antifungal and immunosuppressant activities (1). Rapamycin forms a complex with the immunophilin FKBP12 which then inhibits the activity of FRAP/ mTOR (TOR in yeast) (2,3). Rapamycin treatment of cells leads to the dephosphorylation and inactivation of p70 S6 kinase. Rapamycin also leads to the dephosphorylation of 4E-BP1/PHAS1, thereby promoting its binding to and inactivation of eIF4E (4,5). This activity has been shown to be the basis for Rapamycin's ability to block protein synthesis and to arrest cell cycle progression in the G1-phase (6,7). However, it has been suggested that Rapamycin's inhibition of the G1/S transition may be the consequence of its effect on cyclin D1 mRNA and protein stability (8).
Background: MEK1 and MEK2, also called MAPK or Erk kinases, are dual-specificity protein kinases that function in a mitogen activated protein kinase cascade controlling cell growth and differentiation (1-3). Activation of MEK1 and MEK2 occurs through phosphorylation of two serine residues at positions 217 and 221, located in the activation loop of subdomain VIII, by Raf-like molecules. MEK1/2 is activated by a wide variety of growth factors and cytokines and also by membrane depolarization and calcium influx (1-4). Constitutively active forms of MEK1/2 are sufficient for the transformation of NIH/3T3 cells or the differentiation of PC-12 cells (4). MEK activates p44 and p42 MAP kinase by phosphorylating both threonine and tyrosine residues at sites located within the activation loop of kinase subdomain VIII.
Background: Calyculin A inhibits the activity of protein phosphatases PP1 and PP2A (1,2). Unlike Okadaic acid, which reduces PP2A activity but has little effect on PP1 activity, Calyculin A inhibits both phosphatases (1). Neither Calyculin A nor Okadaic acid inhibit acid or alkaline phosphatases or phospho- tyrosine protein phosphatases (2).
Background: LY294002 was shown to act in vivo as a highly selective inhibitor of phosphatidylinositol 3 (PI3) kinase. When used at a concentration of 50 μM, it specifically abolished PI3 kinase activity (IC50=0.43 μg/ml; 1.40 μM) but did not inhibit other lipid and protein kinases such as PI4 kinase, PKC, MAP kinase or c-Src (1). LY294002 is soluble in DMSO or ethanol. For use with in vitro or cell-based assays, it may be diluted into aqueous buffers to yield the desired concentrations. For experiments with cultured cells, CST recommends treating the cells with LY294002 for one hour prior to, and for the duration of, the stimulation. LY294002 has been shown to block PI3 kinase-dependent Akt phosphorylation and kinase activity.
Application Methods: Immunoprecipitation, Western Blotting
Background: Cyclooxygenase1 (Cox1) and cyclooxygenase2 (Cox2), family members with 60% homology in humans, catalyze prostaglandin production from arachidonic acid (1,2). While Cox1 expression is constitutive in most tissues, Cox2 expression is induced by lipopolysaccharide (LPS) and peptidoglycan (PGN) (3). PGN activates Ras, leading to phosphorylation of Raf at Ser338 and Erk1/2 at Tyr204. The activation of MAP kinase signaling results in subsequent activation of IKKα/β, phosphorylation of IκBα at Ser32/36, and NF-κB activation. Finally, activation of the transcription factor NF-κB is responsible for the induction of Cox2 expression (4). Investigators have shown that LPS and PGN induce the clinical manifestations of arthritis and bacterial infections, such as inflammation, fever, and septic shock (5). Research studies have indicated that Cox1 and Cox2 may also play a role in the neuropathology of Alzheimer's disease by potentiating γ-secretase activity and β-amyloid generation (6).
Application Methods: Immunofluorescence (Immunocytochemistry), Immunoprecipitation, Western Blotting
Background: PZR (Protein zero related) is an immunoglobulin superfamily protein that specifically binds the tyrosine phosphatase SHP-2 through its intracellular immunoreceptor tyrosine-based inhibitory motifs (ITIMs) (1,2). PZR is phosphorylated by c-Src, c-Fyn, c-Lyn, Csk, and c-Abl (3). PP1, a Src family kinase inhibitor, inhibits PZR phosphorylation (4,5). There are three alternatively spliced isoforms, designated as PZR, PZRa, and PZRb; both PZRa and PZRb lack ITIMs (6,7). PZR is the main receptor of ConA and has an important role in cell signaling via c-Src (4). PZR is expressed in many cell types and is localized to cell contacts and intracellular granules in BAECs and mesothelioma (REN) cells. PZR has been implicated as a cell adhesion protein that may be involved in SHP-2-dependent signaling at interendothelial cell contacts (3). Hypertyrosine phosphorylation of PZR was observed during embryogenesis in a mouse model of Noonan syndrome (8).
Application Methods: Flow Cytometry, Immunofluorescence (Immunocytochemistry), Immunoprecipitation, Western Blotting
Background: Next to BRCA1 gene 1 (NBR1) protein is known for its encoding gene proximity to the BRCA1 tumor suppressor gene (1,2). N-terminal Phox and Bem1p (PB1) domains of NBR1 mediate its interaction with muscle specific titin kinase (3,4) and scaffolding protein p62 (4). NBR1 plays a role in autophagy by facilitating the autophagosomal degradation of ubiquitinated proteins independently and also in concert with p62 (5,6).
Application Methods: Immunohistochemistry (Paraffin), Western Blotting
Background: Amyloid β (Aβ) precursor protein (APP) is a 100-140 kDa transmembrane glycoprotein that exists as several isoforms (1). The amino acid sequence of APP contains the amyloid domain, which can be released by a two-step proteolytic cleavage (1). The extracellular deposition and accumulation of the released Aβ fragments form the main components of amyloid plaques in Alzheimer's disease (1). APP can be phosphorylated at several sites, which may affect the proteolytic processing and secretion of this protein (2-5). Phosphorylation at Thr668 (a position corresponding to the APP695 isoform) by cyclin-dependent kinase is cell-cycle dependent and peaks during G2/M phase (4). APP phosphorylated at Thr668 exists in adult rat brain and correlates with cultured neuronal differentiation (5,6).
Background: Docetaxel belongs to the taxane family of antitumor and antileukemic agents (1). A microtubule-stabilizing agent, docetaxel acts as an inhibitor of cellular functions that require microtubule dynamics including cell division, and is now in use as a treatment for breast, prostate and lung cancer (2).
Background: Roscovitine is a cell permeable reversible selective inhibitor of cyclin-dependent kinases CDK1 (cdc2), CDK2 and CDK5 (1). A purine analog, this drug competes for the binding site of ATP in the catalytic cleft. Treatment of cultured cells with roscovitine can cause cell cycle arrest or apoptosis (1-4). The IC50 for cdc2 activity is 0.65 μM in vitro (1).
Application Methods: Immunofluorescence (Immunocytochemistry), Western Blotting
Background: Numb contains an amino-terminal phosphotyrosine-binding (PTB) domain and carboxy-terminal endocytic binding motifs for α-adaptin and EH (Eps15 homology) domain-containing proteins, indicating a role in endocytosis (1,2). There are four mammalian Numb splicing isoforms that are differentially expressed and may have distinct functions (3-5). Numb acts as a negative regulator of Notch signaling by promoting ubiquitination and degradation of Notch (6). The protein is asymmetrically segregated into one daughter cell during cell division, producing two daughter cells with different responses to Notch signaling and different cell fates (7,8). The localization of Numb can also be regulated by G-protein coupled receptor (GPCR) and PKC signaling (9).
|Human, Monkey, Mouse, Rat|
Application Methods: Immunofluorescence (Immunocytochemistry), Immunoprecipitation, Western Blotting
Background: DDX5 (DEAD box polypeptide 5), also known as p68, was first identified as a 68 kDa nuclear protein with similarity to translation initiation factor eIF-4A (1). DDX5 is a member of the DEAD box family of putative RNA helicases, defined by the presence of a conserved DEAD (Asp-Glu-Ala-Asp) motif that appears to function primarily in the regulation of RNA secondary structure. DDX5 exhibits ATP-dependent RNA helicase activity (2) and has been identified as a critical subunit of the DROSHA complex that regulates miRNA and rRNA processing (3,4). DDX may also regulate mRNA splicing (5) and has been shown to interact with HDAC1, where it can regulate promoter-specific transcription (6). DDX5 interacts with a diverse group of proteins, including Runx2, p53, Smad3, CBP, and p300 (7-10), suggesting an important role for DDX5 in a multitude of developmental processes. Notably, DDX5 may be involved in growth factor-induced epithelial mesechymal transition (EMT). Phosphorylation of DDX5 at Tyr593 following PDGF stimulation was shown to displace Axin from β-catenin; this prevented phosphorylation of β-catenin by GSK-3β, leading to Wnt-independent nuclear translocation of β-catenin (11) and increased transcription of c-Myc, cyclin D1, and Snai1 (12,13).
Application Methods: Immunofluorescence (Immunocytochemistry), Western Blotting
Background: IRAP (also known as LNPEP) was originally described as an insulin-responsive aminopeptidase found in Glut4-containing vesicles (1). It is essentially always in the same compartments as Glut4 and has identical insulin-stimulated translocation patterns as Glut4 (2). IRAP is therefore considered to be a surrogate marker for Glut4 (2). IRAP was later found to be a critical enzyme that regulates the expression and activity of several essential hormones and regulatory proteins, including the Glut4 transporter (3,4). This membrane associated, zinc-dependent cystinyl aminopeptidase acts as both a receptor for angiotensin IV as well as the enzyme that catalyzes the synthesis of this essential hormone from its angiotensinogen precursor (5). IRAP catalyzes the hydrolysis of several peptide hormones, including oxytocin and vasopressin (4). Abnormal IRAP expression or activity is associated with several forms of cancer in humans, including renal and endometrial cancers (6,7).
|All Species Expected, Human, Monkey, Mouse, Rat|
Application Methods: Western Blotting
Background: A distinct form of protein glycosylation, beta-linked N-acetyl-glucosamine (GlcNAc) moieties can be added to serine or threonine residues of proteins (1,2). This differs from other forms of glycosylation, as it typically is a single moiety rather than the complex branched sugars that are more commonly studied. It is thought that these modifications happen in a much more dynamic cycle more reminiscent of phosphorylation modifications (3). GlcNAc modified proteins are found in the cytoplasm and nucleus and are modulated by means of specific O-GlcNAc transferases (OGT) as well as GlcNAcase activity that can be inhibited using the Thiamet-G (TMG) inhibitor. Mass spectrometry analysis of this modification has been complicated due to the loss of the GlcNAc group during ionization and fragmentation, but methods and technologies such as electron transfer dissociation (ETD) are opening up new avenues to study these modifications. O-GlcNAc could play an important role in many cellular processes, including metabolism, growth, morphogenesis, apoptosis, transcription, and it may play a critical role in cancer.(4)