PhosphoPlus^® Duets from Cell Signaling Technology (CST) provide a means to assess protein activation status. Each Duet contains an activation-state and total protein antibody to your target of interest. These antibodies have been selected from CST's product offering based upon superior performance in specified applications.

Neurogenic differentiation factor 1 (NeuroD1) is a member of the basic helix-loop-helix (bHLH) family of transcription factors. These proteins function by forming heterodimers with E-proteins and binding to the canonical E-box sequence CANNTG (1,2). Neuronal activity results in CaMKII-mediated phosphorylation of NeuroD1 at Ser336, which is necessary for dendrite formation and growth (3,4). NeuroD1 is also phosphorylated at Ser274, though the results are context dependent, as phosphorylation by Erk stimulates NeuroD1 activity in pancreatic β cells while phosphorylation by GSK-3β inhibits NeuroD1 in neurons (3). NeuroD1 is crucially important in both the pancreas and the developing nervous system and plays a large role in the development of the inner ear and mammalian retina (3). Mice lacking NeuroD1 become severely diabetic and die shortly after birth due to defects in β cell differentiation (2,3,5,6). The lack of NeuroD1 in the brain results in severe defects in development (5). Human mutations have been linked to a number of types of diabetes, including type I diabetes mellitus and maturity-onset diabetes of the young (1,3).

Erk1/2 kinase activity is stimulated by glucose and calcium influx in pancreatic beta cells, and the subsequent phosphorylation of NeuroD1 at Ser274 promotes insulin gene transcription (7,8). Phosphorylated NeuroD1 in the pancreas is increasingly translocated to the nucleus, where it directly interacts with the insulin promoter (9). Active, nuclear NeuroD1 acts in synergy with Pdx1 to activate insulin, NKX2.2, and islet amyloid polypeptide (IAPP) transcription while suppressing Pdx1-driven transcription of somatostatin (10,11). In developing rat pineal gland, phosphorylation of NeuroD1 at Ser274 and Ser336 is tightly correlated with NeuroD1 nuclear localization, and cytoplasmic to nuclear shuttling of the protein is under cyclical day and night adrenergic control (12). In 293T cells, transfection of a nonphosphorylatable Ser274Ala mutant blocked NeuroD1 ubiquitination and proteasomal degradation (13). The localization of phosphorylated NeuroD1 is reversed in these cells compared to pancreatic beta cells, with a Ser274Glu phospho-mimic localized primarily to the cytoplasm in the former, further evidence of the context-specific nature of this modification. (13).