p42

p42 is a designation used in biology and other disciplines to refer to several distinct entities, most notably a 42-kilodalton mitogen-activated protein kinase known as p42 MAP kinase or ERK2. In the MAPK signaling cascade, ERK2 is activated by dual phosphorylation of the TEY activation loop by the kinases MEK1/2. Once active, ERK2 translocates to the nucleus and phosphorylates transcription factors such as ELK1, leading to changes in gene expression that regulate cell proliferation, differentiation, and survival. ERK2 activity is regulated by upstream signals from receptor tyrosine kinases and RAS-MAPK modules, and it can engage in cross-talk with other signaling pathways.

Clinical relevance: Aberrant ERK2 signaling is implicated in several cancers and developmental disorders. Therapeutic strategies include MEK inhibitors and direct ERK inhibitors aimed at reducing pathway activity.

Other uses: The symbol p42 may be used in various publications to denote other 42-kilodalton proteins identified in different species or experimental contexts. The exact identity must be inferred from accompanying gene or protein names or experimental descriptions. In many cases, p42 is paired with p44 MAPK, which refers to ERK1, its close homolog in the same pathway.

See also: p44 MAPK; MAPK signaling pathway.