Serine/threonine-protein kinase MRCK beta

Serine/threonine-protein kinase MRCK beta (encoded by CDC42BPB) is a downstream effector of CDC42 that regulates cytoskeleton reorganization and cell migration through phosphorylation of substrates including PPP1R12C, MYL9, and PPP1R12A (UniProt: Q9Y5S2). In concert with accessory proteins, it modulates lamellar actomyosin dynamics and lamellipodial F-actin organization, processes essential for cell protrusion.

The protein is associated with Chilton-Okur-Chung neurodevelopmental syndrome (CHOCNS; MIM 619841), a disorder characterized by developmental delay, intellectual disability, hypotonia, and brain structural abnormalities; many patients exhibit autism spectrum disorder and behavioral difficulties (UniProt: Q9Y5S2).

In Alzheimer's Disease, MRCK beta is consistently downregulated in post-mortem AD brain tissue compared to age-matched controls, with a mean log2 fold-change of −0.456 (Chaparral AD proteomics). This reduction was observed across subcellular fractions in TMT-labeled quantitative proteomics analysis, suggesting potential involvement of impaired cytoskeletal dynamics in AD pathology.