Technical library

AKT, also referred to as PKB or Rac, plays a critical role in controlling survival and apoptosis. This protein kinase is activated by insulin and various growth and survival factors to function in a Wortmannin-sensitive pathway involving PI3 kinase. Activation at Thr309 and Ser473 are the main activating phosphorylation events for AKT. The main isoforms identified so far are AKT1, 2 and 3. AKT3 is mainly expressed in the brain. AKT1 and 2 play differential roles in glucose homeostasis. Our data show increased phosphorylation of AKT using a phospho-Ser743 specific antibody. This antibody is believed to recognize phospho-Ser473 on all three AKT isoforms (see Cell Signaling Technologies data sheet).

The human housekeeping protein Delta-aminolevulinate Synthase catalyzes the condensation of glycine with succinyl-CoA to form delta-aminolevulinic acid. It is represented in the Nanopro assay by two peaks at pI's around 5.6 and 5.9. Our data show its utility as a loading control for EGF stimulation in HeLa and MCF10A cells.

GSK3 is a critical downstream element of the PI3 kinase/AKT cell survival pathway whose activity can be inhibited by AKT-mediated phosphorylation at Ser21 of GSK-3α and Ser9 of GSK-3β. While GSK-3α and GSK-3β have high sequence homology, their biological function differs. The data presented shows an increase of peaks detected by anti-phospho GSK-3β antibody as well as an increase of the same peaks detected by the total anti-GSK-3β antibody in response to EGF treatment in MCF10A cells. At the same time, the peaks not recognized by the anti-phospho Ser21 antibody decrease in size, implying that these peaks represent non-phospho or non-pS21 phospho GSK-3α forms. The position of these peaks around pI 9 is in accordance with the theoretical pI for this sequence. Alignment of the GSKα and GSKβ profiles, in addition to use of antibodies recognizing both isoforms, confirmed the specificity of the anti-GSK-3α versus the anti-GSK-3β antibodies used (data not shown).

The 70 kilodalton heat shock proteins (Hsp70) are a family of ubiquitously expressed heat shock proteins. Proteins with similar structure exist in virtually all living organisms. The Hsp70s are an important part of the cell's machinery, and help to protect proteins from misfolding under stress. We show an increase of Hsp-70 expression in response to heat shock at 42°C in A549 cells.

Caspases 3 exists as an inactive proenzyme that undergoes proteolytic processing at conserved aspartic residues to produce two subunits, large and small, that dimerize to form the active enzyme. Its activation is an important apoptosis marker. The data shows increased signal with antibodies specific to the Caspase 3 p17 subunit in response to apoptosis induction through prolonged treatment of K562 cells with Iminatib (aka Gleevec®) at expected pI's around 6.3-6.5.

The Signal Transducer and Activator of Transcription (STAT) proteins regulate many aspects of cell growth, survival and differentiation. The transcription factors in this family are activated by Janus Kinase (JAK). Dysregulation of this pathway is frequently observed in primary tumors and leads to increased angiogenesis, enhanced survival of tumors and immunosuppression. STAT3 is constitutively active in overexpressing BCR-ABL K562 myelogenous leukaemia cells. Imatinib (also known as Gleevec®), a BCR-ABL inhibitor, reduces STAT3 phosphorylation in these cells. STAT3 is also part of the Epidermal Growth Factor (EGF) signaling cascade as shown in MCF10A cells.

Phospholipase C (PLC) catalyzes the hydrolysis of phosphatidylinositol 4, 5-bisphosphate (PIP2) to produce the metabolite second messenger molecules inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG). Increase of IP3 results in elevated intracellular free Ca2+. PLC's are activated through G-protein coupled receptor stimulation as well as tyrosine receptor kinase activation and therefore bridge both important signaling pathways. The family of PLC's consists of 12 isoforms with different roles in signaling. For example, PLCγ1 forms a complex with activated EGF receptors, which leads to the phosphorylation of PLCγ at Tyr771, 783 and 1245. Here we detect the phosphorylation of PLCγ1 in HEK293 cells in response to EGF treatment.

Dual specificity mitogen-activated protein kinases (MEK) are members of the dual specificity protein kinase family, which act upstream from the classical MAP kinases through phosphorylation and thus activation of ERK1 and 2 in response to a wide variety of extra- and intracellular signals. While the functions of MEK1 and MEK2 are very similar, these kinases differ significantly in the way they are regulated. For example, serum addition can specifically induce MEK1 activity in CHO cells. By contrast, MEK2 appears to be the functionally predominant isoform in formyl-methionyl-leucyl-phenylalanine treated neutrophils. Here we show MEK1 activation in MCF10A cells treated with EGF.

Src is involved in regulating growth and differentiation in eukaryotic cells. Src activity is regulated by tyrosine phosphorylation at two sites, but with opposing effects. Phosphorylation of Tyr416 in the activation loop of the kinase domain by Csk upregulates enzyme activity, whereas phosphorylation of Tyr529 in the carboxy-terminal tail renders the enzyme less active. We evaluated Src response to EGF in A431 cells.

p27, also known as Kip1, is a cell cycle regulatory/inhibitory protein. It is similar to other members of the "Cip/Kip" family which includes the p21Cip1/Waf1 and p57Kip2 genes. p27 shares their functional characteristic of being able to bind several different classes of Cyclin and CDK molecules, acting as a CDK inhibitor. We show the response of p27 to EGF treatment in MCF10A cells.

Translation repressor protein 4E-BP inhibits cap-dependent translation by binding to the eIF4E translation initiation factor. Hyperphosphorylation of 4E-BP disrupts this interaction and results in activation of cap-dependent translation. Both the PI3 kinase/AKT pathway and FRAP/mTOR kinase regulate 4E-BP activity. 4E-BP1 has been implicated as a biomarker for several cancer types, while 4E-BP2 has been shown to potentially play a role in energy homeostasis. We show 4E-BP2 activation in MCF10A cells in response to EGF and 4E-BP2 inhibition in MCF7 cells with LY294002 (PI3 kinase inhibitor).

Epitope tags are widely used for afinity purification as well as for highly sensitive detection of recombinant proteins. The c-Myc-tag
consists of a short peptide sequence (MEEQKLISEEDLLM). EGFP was expressed with a c-Myc-tag at either the C- or N-terminus of the
protein. As expected from the amino acid composition of this tag, a slight acidic shift in the pI of the tagged protein can be observed.

Epitope tags are widely used for afinity purification as well as for highly sensitive detection of recombinant proteins. The HA-tag consists of a short peptide sequence (MAYPYDVPDYASM). Here, EGFP was expressed with a HA-tag at both the C- and N-terminal of the protein. As expected from the amino acid composition of this tag, a slight acidic shift in the pI of the tagged protein can be observed.

In many different species, lactate dehydrogenase (LDH) constitutes a major checkpoint of anaerobic glycolysis by catalyzing the reduction of pyruvate into lactate. LDH in its native form, is a tetramer of LDHA (calculated pI: 8.4) and LDHB (calculated pI: 5.7) proteins in different combinations. When the number of protein B over protein A increases, isozymes become more efficient in catalyzing the oxidation of lactate to pyruvate. LDH overexpression has been implicated in the pathogenesis and progression of many cancers and may constitute a valid therapeutic target for diseases.

Green Fluorescent Protein (GFP) was originally isolated from jellyfish and exhibits a bright green fluorescence when exposed to blue light. In cell and molecular biology, GFP is commonly utilized as a reporter of protein expression. GFP can be introduced and its expression maintained in a wide range of cell lines and organisms. Thus, assays suitable for GFP detection offer useful tools for following the expression of proteins for which high affinity antibodies are lacking. The data demonstrates identification of a highly sensitive antibody for GFP detection via NanoPro assay.

Mitofusin 1 (Mfn1) and Mitofusin 2 (Mfn2) are two highly homologous mitochondrial outer membrane proteins necessary for mitochondrial fusion. Mitochondrial fusion is necessary to maintain mitochondrial health and function, and mitochondrial dysfunction is implicated in diseases such as Charcot-Marie-Tooth 2A and dominant optic atrophy, as well as in multiple tissue types. Phosphorylation of these proteins has not been widely studied. Our data show detectoin of Mfn1 protein in three neuronal tissues: retina, optic nerve, and the superior colliculus region of the brain in a mouse model, DBA/2J, a widely accepted model for glaucoma.

Survivin, an inhibitor of apoptosis protein (IAP) is a pro-survival molecule that is increased in nearly every human tumor studied. In head and neck squamous cell carcinoma, Survivin levels are significantly greater than in normal upper aerodigestive mucosa. High Survivin levels in these tissues correlate with a higher probability of nodal metastasis and loco-regional recurrence, but may also indicate higher radiosensitivity. Survivin includes multiple sites for post-translational modification, including 4-5 major phosphorylation sites.

GAPDH (Glyceraldehyde-3-phosphate dehydrogenase) is a housekeeping gene found in most tissues and cells. Because GAPDH expression is fairly constant in a variety of tissue and cell types, this protein is often used as a control in comparisons of protein expression levels. Here, we describe its use as a loading control for cIAP1 inhibition in PBMCs. In the NanoPro assay, GAPDH is present with a major peak around pI 8.9 under the conditions described. We also demonstrate the multiplexing capabilities of the NanoPro assay and the detection of cIAP1 and GAPDH in the same capillary.

Modulation of chromatin structure plays an important role in the regulation of transcription in eukaryotes. The nucleosome, made up of DNA wound around eight core histone proteins (two each of H2A, H2B, H3, and H4), is the primary building block of chromatin (1). The amino-terminal tails of core histones undergo various post-translational modifications, including acetylation, phosphorylation, methylation, and ubiquitination (2-5). These modifications occur in response to various stimuli and have a direct effect on the accessibility of chromatin to transcription factors and, therefore, gene expression (6). In most species, histone H2B is primarily acetylated at Lys5, 12, 15, and 20 (4,7). Histone H3 is primarily acetylated at Lys9, 14, 18, 23, 27, and 56. Acetylation of H3 at Lys9 appears to have a dominant role in histone deposition and chromatin assembly in some organisms (2,3). Phosphorylation at Ser10, Ser28, and Thr11 of histone H3 is tightly correlated with chromosome condensation during both mitosis and meiosis (8-10). Phosphorylation at Thr3 of histone H3 is highly conserved among many species and is catalyzed by the kinase haspin. Immunostaining with phospho-specific antibodies in mammalian cells reveals mitotic phosphorylation at Thr3 of H3 in prophase and its dephosphorylation during anaphase (11).