Phosphoinositide-3-kinase regulatory subunit 1 and Signal transducer and activator of transcription 3 (PIK3R1 / STAT3)

Phosphoinositide-3-kinase regulatory subunit 1 (PIK3R1) and Signal transducer and activator of transcription 3 (STAT3) are essential proteins in intracellular signaling pathways that govern cell growth, survival, and immune responses [UniProt]. PIK3R1 acts as the p85α regulatory subunit of the Class IA PI3K complex, where it binds to phosphorylated tyrosine residues on activated receptors to recruit and regulate the p110 catalytic subunit [NCBI Gene]. STAT3 is a transcription factor that is activated by phosphorylation, typically via Janus kinases (JAKs) in response to cytokine signaling, and subsequently translocates to the nucleus to drive the expression of genes involved in cell cycle progression and anti-apoptosis [StatPearls]. Both proteins are frequently implicated in human diseases; PIK3R1 mutations are common in various cancers, while STAT3 is often constitutively active in tumors and involved in inflammatory disorders [PubMed]. The specific mention of these proteins in relation to danicamtiv, a cardiac myosin activator, highlights that they are not directly modified by the drug, which is a key finding in establishing the selectivity of danicamtiv for cardiac muscle contractility over general signaling pathways [PubChem]. This distinction is important for the safety profile of danicamtiv, as it avoids the systemic metabolic and immunological side effects associated with the direct modulation of PI3K or STAT3 signaling [ClinicalTrials.gov].

Other names

p85-alphaGRB1p85APRFHIESSignal transducer and activator of transcription 3Phosphoinositide-3-kinase regulatory subunit 1

PIK3R1 is targeted via the inhibition of the PI3K catalytic complex (p110), while STAT3 is targeted by inhibiting its phosphorylation, dimerization, or DNA binding.