C/EBP Antibody Sampler Kit #12814

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).