Phospho-SMAD1/5 (Ser463/465) Recombinant Rabbit mAb (S-4058)

Phospho-SMAD1/5 (Ser463/465) is a key activated transcriptional regulator in the Bone Morphogenetic Protein (BMP) signaling pathway. When BMP ligands bind to type I and type II serine/threonine kinase receptors on the cell membrane, the activated receptor complex specifically phosphorylates the serine residues at position 463 (in SMAD1) and 465 (in SMAD5) within the C-terminal SXS motif of SMAD1 or SMAD5 proteins. This phosphorylation event is the central step in SMAD1/5 activation, prompting them to form a heterotrimeric complex with the common mediator SMAD4 and translocate into the nucleus. There, they regulate the transcription of downstream target genes (such as Id1, Id2, etc.), mediating the crucial role of BMP signaling in various biological processes including cell proliferation, differentiation, apoptosis, as well as embryonic development, bone formation, and homeostasis maintenance. The phosphorylation level at this site serves as a classic molecular marker for assessing the activity of the BMP/SMAD pathway.