Phospho-ULK1 (Ser555) Recombinant Rabbit mAb (S-3440)

Phospho-ULK1 (Ser555) refers to the phosphorylated form of the key autophagy-initiating kinase ULK1 (Unc-51-like kinase 1) at the serine 555 residue. This specific modification is primarily catalyzed by AMP-activated protein kinase (AMPK) under conditions of cellular energy stress, such as glucose deprivation or hypoxia. When AMPK senses energy depletion and is itself activated by phosphorylation at Thr172, it phosphorylates ULK1 at Ser555. This event promotes the dissociation of ULK1 from its inhibited state bound to mTORC1 and facilitates its translocation to organelles like mitochondria, thereby initiating autophagy (including mitophagy) and lipophagy. Consequently, phosphorylation at Ser555 is recognized as a crucial positive regulatory signal for ULK1 activation and the initiation of the autophagy pathway, playing a central role in cellular adaptation to metabolic stress and the maintenance of energy homeostasis. Researchers commonly use specific phospho-specific antibodies (e.g., against P-Ser555 ULK) in techniques like Western Blotting to detect the phosphorylation level at this site, which serves as an indicator of intracellular autophagic activity.