The C/EBP Antibody Sampler Kit provides an economical means of evaluating the C/EBP family of transcription factors and several phosphorylation sites that are involved in its activation. The kit includes enough antibody to perform two western blot experiments with each primary antibody.
Specificity / Sensitivity
Unless otherwise indicated, each antibody will recognize endogenous total levels of their target protein. Each activation state antibody recognizes the phosphorylated form of its target. Phospho-C/EBPβ (Thr235) Antibody recognizes endogenous levels of human liver activating protein (LAP) only when phosphorylated at Thr235, mouse and rat LAP only when phosphorylated at Thr188, and liver inhibitory protein (LIP) only when phosphorylated at Thr37. The C/EBPβ (LAP) Antibody detects endogenous levels of total C/EBPβ, the p38 and p36 LAPs, but not the p20 LIP.
Source / Purification
Polyclonal antibodies are produced by immunizing animals with a synthetic phosphopeptide corresponding to residues surrounding Ser21 of human C/EBPα, Thr222/226 of mouse C/EBPα, or Thr235 of human C/EBPβ. Polyclonal antibodies are also produced by immunizing animals with a synthetic peptide corresponding to the amino-terminal sequence of human C/EBPβ or the sequence of mouse C/EBPδ. Polyclonal antibodies are purified by protein A and peptide affinity chromatography. Monoclonal antibodies are produced by immunizing animals with a synthetic peptide corresponding to residues surrounding Ala176 of human C/EBPα protein or to residues surrounding Leu159 of human CHOP protein.
CCAAT/enhancer-binding proteins (C/EBPs) are transcription factors critical for cellular differentiation, terminal function, and inflammatory response. Six characterized family members (C/EBPα, β, δ, γ, ε, and ζ) are distributed in a variety of tissues (1). Translation from alternative start codons results in two C/EBPα isoforms (p42 and p30) that are strong transcriptional activators (2). Research studies indicate that insulin and insulin-like growth factor-I stimulate C/EBPα dephosphorylation, which may play a key role in insulin-induced repression of GLUT4 transcription (3). Phosphorylation of C/EBPα at Thr222, Thr226, and Ser230 by GSK-3 may be required for adipogenesis (4). The two forms of C/EBPβ, 38 kDa liver activating protein (LAP) and the 20 kDa liver inhibitory protein (LIP), may result from alternative translation. The 38 kDa LAP protein is a transcriptional activator while LIP may inhibit C/EBPβ transcriptional activity (5). Phosphorylation of C/EBPβ at distinct sites stimulates its transcriptional activity (6-8). Phosphorylation at the rat-specific site Ser105 in C/EBPβ appears essential for C/EBPβ activation in rat (9). C/EBPδ protein is highly expressed in adipose tissue, lung, and intestine (10). Increased expression of C/EBPδ mRNA levels during adipogenesis suggests that C/EBPδ plays an important role in positively regulating adipogenesis (10,11). C/EBPδ is expressed in the mammalian nervous system and plays an important role in long-term memory (10,12). CHOP is a C/EBP-homologous protein that inhibits C/EBP and LAP in a dominant-negative manner (13). CHOP expression is induced by cellular stresses, including starvation; induced CHOP suppresses cell cycle progression from G1 to S phase (14). During ER stress, the level of CHOP expression is elevated and CHOP functions to mediate programmed cell death (15).