Background: The epidermal growth factor (EGF) receptor is a transmembrane tyrosine kinase that belongs to the HER/ErbB protein family. Ligand binding results in receptor dimerization, autophosphorylation, activation of downstream signaling, internalization, and lysosomal degradation (1,2). Phosphorylation of EGF receptor (EGFR) at Tyr845 in the kinase domain is implicated in stabilizing the activation loop, maintaining the active state enzyme, and providing a binding surface for substrate proteins (3,4). c-Src is involved in phosphorylation of EGFR at Tyr845 (5). The SH2 domain of PLCγ binds at phospho-Tyr992, resulting in activation of PLCγ-mediated downstream signaling (6). Phosphorylation of EGFR at Tyr1045 creates a major docking site for the adaptor protein c-Cbl, leading to receptor ubiquitination and degradation following EGFR activation (7,8). The GRB2 adaptor protein binds activated EGFR at phospho-Tyr1068 (9). A pair of phosphorylated EGFR residues (Tyr1148 and Tyr1173) provide a docking site for the Shc scaffold protein, with both sites involved in MAP kinase signaling activation (2). Phosphorylation of EGFR at specific serine and threonine residues attenuates EGFR kinase activity. EGFR carboxy-terminal residues Ser1046 and Ser1047 are phosphorylated by CaM kinase II; mutation of either of these serines results in upregulated EGFR tyrosine autophosphorylation (10).
Background: Senescence is characterized by stable stress-induced proliferative arrest and resistance to mitogenic stimuli, as well as the secretion of proteins such as cytokines, growth factors and proteases. These secreted proteins comprise the senescence-associated secretory phenotype (SASP). Senescent cells are thought to accumulate as an organism ages, and contribute to age-related diseases, including cancer, through promotion of inflammation and disruption of normal cellular function (1,2). The composition of the SASP varies, and SASP components can be either beneficial or deleterious in human disease, depending on the context (3).Senescence Associated Secretory Phenotype (SASP) Antibody Sampler Kit provides a collection of antibodies to various SASP components, including TNF-alpha, interleukin-6 (IL-6), the multifunctional cytokine IL-1beta, the chemokines CXCL10, RANTES/CCL5 and MCP-1, the matrix metalloprotease MMP3, and the serine-protease inhibitor PAI-1.
Background: Senescence is characterized by stable stress-induced proliferative arrest and resistance to mitogenic stimuli, as well as the secretion of proteins such as cytokines, growth factors and proteases. These secreted proteins comprise the senescence-associated secretory phenotype (SASP). Senescent cells are thought to accumulate as an organism ages, and contribute to age-related diseases, including cancer, through promotion of inflammation and disruption of normal cellular function (1,2).Because there is no single biomarker that can be used to definitively identify senescent cells, researchers must rely on a collection of biomarkers commonly associated with senescence. The Senescence Marker Antibody Sampler Kit provides a collection of antibodies to commonly used biomarkers of senescence-associated cell cycle arrest (p16 INK4A, p21 Waf1/Cip1), senescence-associated DNA damage (gamma-Histone H2A.X), and the SASP (HMGB1, IL-6, TNF-alpha, MMP3). The kit also includes an antibody to Lamin B1, which is frequently reduced in senescent cells.
Background: The mammalian target of rapamycin (mTOR, FRAP, RAFT) is a Ser/Thr protein kinase (1-3) that functions as an ATP and amino acid sensor to balance nutrient availability and cell growth (4,5). When sufficient nutrients are available, mTOR responds to a phosphatidic acid-mediated signal to transmit a positive signal to p70 S6 kinase and participate in the inactivation of the eIF4E inhibitor, 4E-BP1 (6). These events result in the translation of specific mRNA subpopulations. mTOR is phosphorylated at Ser2448 via the PI3 kinase/Akt signaling pathway and autophosphorylated at Ser2481 (7,8). mTOR plays a key role in cell growth and homeostasis and may be abnormally regulated in tumors. For these reasons, mTOR is currently under investigation as a potential target for anti-cancer therapy (9).
Background: One-carbon metabolism includes various enzymatic reactions involving the transfer of one-carbon groups mediated by folate cofactor (1). The activated one-carbon groups are used by various metabolic pathways, including purine synthesis, thymidine synthesis, and remethylation of homocysteine to methionine (1). S-adenosylhomocysteine hydrolase-like protein 1 (AHCYL1) is a member of the S-adenosylhomocysteine hydrolase family, which participates in the metabolism of S-adenosyl-L-homocysteine (2). Cystathionine beta-synthase (CBS) is a key enzyme involved in sulfur amino acid metabolism as it catalyzes the formation of cystathionine from serine and homocysteine (3,4). Cystathionine γ-lyase (CGL) is an enzyme in the transsulfuration pathway, a route in the metabolism of sulfur-containing amino acids (5). Methylenetetrahydrofolate reductase (MTHFR), a key enzyme in one-carbon metabolism, catalyzes the conversion of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate (1). 5-methyltetrahydrofolate donates its methyl group for remethylation of homocysteine to methionine (1). Methionine is further converted to S-adenosylmethionine (SAM), a major reactive methyl carrier (1). NADP+ dependent methylenetetrahydrofolate dehydrogenase 1-like (MTHFD1L) is a mitochondrial enzyme that catalyzes the production of formate from 10-formyl-tetrahydrofolate in one-carbon flow from mitochondria to cytoplasm (6,7). MTHFD2 is a bifunctional methylenetetrahydrofolate dehydrogenase/cyclohydrolase involved in mitochondrial folate metabolism (8). Serine hydroxymethyltransferase 1 (SHMT1) is a cytoplasmic serine hydroxylmethyltransferase (9,10). It catalyzes the conversion of serine to glycine with the transfer of β-carbon from serine to tetrahydrofolate (THF) to form 5, 10-methylene-THF (9, 10). The methylation of deoxyuridine monophosphate (dUMP) to deoxythymidine monophosphate (dTMP) is an essential step in the formation of thymine nucleotides, a process catalyzed by thymidylate synthase (TS or TYMS) (11-13).