The ULK1 Antibody Sampler Kit provides an economical way to investigate ULK1 signaling. The kit contains enough primary antibody to perform two western blots with each primary antibody.
Specificity / Sensitivity
ULK1 (D8H5) Rabbit mAb, Raptor (24C12) Rabbit mAb, and AMPKα (D63G4) Rabbit mAb recognize total endogenous levels of the corresponding target proteins irrespective of phosphorylation state. Phospho-ULK1 (Ser555) (D1H4) Rabbit mAb and Phospho-ULK1 (Ser757) Antibody recognize endogenous levels of ULK1 only when phosphorylated at the indicated residues. Phospho-Raptor (Ser792) Antibody recognizes endogenous levels of raptor only when phosphorylated at Ser792. Phospho-AMPKα (Thr172) (40H9) Rabbit mAb recognizes endogenous levels of AMPKα only when phosphorylated at Thr172.
Source / Purification
Activation-state specific monoclonal antibodies are produced by immunizing animals with a synthetic phosphopeptides corresponding to residues surrounding Ser555 of human ULK1 protein or residues surrounding Thr172 of human AMPKα protein. Monoclonal antibodies are produced by immunizing animals with a synthetic peptides corresponding to human raptor protein, residues surrounding Lys40 of human AMPKα protein, or residues surrounding Arg600 of human ULK1 protein. Activation-state specific polyclonal antibodies are produced by immunizing animals with synthetic phosphopeptides corresponding to residues surrounding Ser757 of human ULK1 protein or residues surrounding Ser792 of human raptor protein. Polyclonal antibodies are purified by protein A and peptide affinity chromatography.
Two related serine/threonine kinases, UNC-51-like kinase 1 and 2 (ULK1, ULK2), were discovered as mammalian homologs of the C. elegans gene UNC-51 in which mutants exhibited abnormal axonal extension and growth (1-4). Both proteins are widely expressed and contain an amino-terminal kinase domain followed by a central proline/serine rich domain and a highly conserved carboxy-terminal domain. The roles of ULK1 and ULK2 in axon growth have been linked to studies showing that the kinases are localized to neuronal growth cones and are involved in endocytosis of critical growth factors, such as NGF (5). Yeast two-hybrid studies found ULK1/2 associated with modulators of the endocytic pathway, SynGAP and syntenin (6). Structural similarity of ULK1/2 has also been recognized with the yeast autophagy protein Atg1/Apg1 (7). Knockdown experiments using siRNA demonstrated that ULK1 is essential for autophagy (8), a catabolic process for the degradation of bulk cytoplasmic contents (9,10). It appears that Atg1/ULK1 can act as a convergence point for multiple signals that control autophagy (11), and can bind to several autophagy-related (Atg) proteins, regulating phosphorylation states and protein trafficking (12-16).
Raptor mediates the binding of mTORC1 to ULK1, which phosphorylates and inhibits ULK1 under nutrient rich conditions. AMPK also associates directly with ULK1 and, upon nutrient deprivation, can readily reverse the inhibitory effect of mTORC1 by phosphorylating raptor and initiating autophagy (17,18).