MAP kinases act as an integration point for multiple biochemical signals, and are involved in a wide variety of cellular processes such as proliferation, differentiation, transcription regulation and development.

In response to extracellular signals, this kinase translocates to the cell nucleus, where it regulates gene expression by phosphorylating, and activating different transcription factors.

Four alternatively spliced transcript variants of this gene encoding two distinct isoforms have been reported.

Consequently, ERK5 inhibitors with improved selectivity (void of the BRD4 off-target effect) such as AX15836[17] and BAY-885[18] were developed and should preferably be used for future pharmacological studies.

[21] Based on a close analog of the ERK5 inhibitor BAY-885[18] the Proteolysis Targeting Chimera[22] (PROTAC) INY-06-061[23] was developed which allows to compare the phenotypes resulting from ERK5 inhibition versus degradation.