Phospho-RSK4 (Ser232) Antibody (YA155)

RSK4 (RPS6KA6) is a member of the p90 ribosomal S6 kinase family and functions as a serine/threonine kinase downstream of MAPK/ERK signaling, while exhibiting distinctive regulatory properties compared with other RSK isoforms^[1][2]. Mechanistically, RSK4 acts as a negative regulator of receptor tyrosine kinase signaling by suppressing fibroblast growth factor (FGF) -RAS-ERK pathway activity and inhibiting ERK-dependent transcriptional responses, thereby contributing to control of cellular proliferation and differentiation^[1][3]. Consistent with this role, RSK4 has been linked to p53-dependent growth arrest and p21-associated cell-cycle regulation, supporting its function in growth suppression and cellular senescence programs^[4][5][6]. In disease settings, altered RSK4 expression has been reported in multiple malignancies, including acute myeloid leukemia, colorectal cancer, endometrial cancer, renal cell carcinoma, breast cancer, and non-small cell lung cancer, highlighting its relevance to tumor biology and cancer progression^[7][8][9]. Compared with other RSK family members that generally require growth-factor stimulation for activation, RSK4 displays constitutive kinase activity under serum-starved conditions and may not participate in identical signaling networks, indicating a unique mode of regulation within the RSK family^[2][8]. For experimental research, RSK4 is therefore widely used as a model for investigating ERK-feedback regulation, p53-associated growth arrest, cellular senescence, and context-dependent tumor suppressor mechanisms^[1][4][5].