ERK

ERK1/2 are related protein-serine/threonine kinases in the Ras-Raf-MEK-ERK cascade, which regulates cell adhesion, cell-cycle progression, migration, survival, differentiation, metabolism, proliferation, and transcription^[1]. Mechanistically, MEK1/2 phosphorylates ERK1/2, enabling ERK-dependent signaling outputs that connect extracellular stimulation to nuclear and cytoplasmic responses^[1]. In cell-cycle research, sustained ERK1/2 activation supports G1-to-S-phase progression and regulates positive and antiproliferative cell-cycle factors^[2]. In disease-relevant models, deregulated ERK1/2 activity associates with developmental syndromes and several human diseases, making pathway output a practical readout for phosphoproteomics and signaling-network studies^[3]. Compared with related isoforms, ERK1 and ERK2 show strong functional redundancy during development, and mouse genetic data indicate that total ERK1/2 activity, rather than strict isoform identity, determines developmental output^[4]. Evolutionary analysis also supports interchangeable ERK1/2 action in tetrapods and highlights total ERK quantity as a relevant experimental variable^[5]. For experimental applications, selective ERK1/2 inhibitors such as SCH772984 exploit a unique ERK1/2 binding site and provide tools for probing kinase activity and pathway dependence^[6]. Clinically oriented studies use ulixertinib as an ERK1/2 inhibitor with preclinical activity in BRAF- and RAS-mutant cancer models^[7].