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.

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).