Targeting PAK1 kinase in neurodevelopmental disorders - dysfunction in signaling mediated by protein kinases is linked with neurodevelopmental delay, intellectual disability, and autism

The National Institute of Child Health and Human Development awarded the University of Washington $100,228 on December 1, 2026, under the Child Health and Human Development Extramural Research Projects program (CFDA 93.865) to conduct research on PAK1 kinase dysfunction in neurodevelopmental disorders.

The research investigates P21-activated kinase 1 (PAK1), a serine-threonine protein kinase whose mutations are associated with intellectual disability, developmental delay, macrocephaly, and seizures. The work focuses on identifying downstream phosphorylation targets of PAK1 and determining how neurodevelopmental disorder-associated PAK1 mutations increase its catalytic activity and contribute to neuropathology. PAK1 regulates cortical development by promoting neural progenitor cell proliferation and neuronal migration, and dysfunction in its signaling pathways is linked to neurodevelopmental delay and autism, yet the molecular mechanisms underlying its neuronal function remain poorly understood and no targeted therapy currently exists for PAK1-associated intellectual disability.

The University of Washington's Office of Sponsored Programs, acting as the grant recipient, will perform work at the institution's Seattle, Washington location. The award covers performance from December 1, 2026, through June 30, 2029. This is a project grant, the standard assistance type for NIH extramural research funding to universities.

P21-activated kinase 1 (PAK1) is a serine-threonine protein kinase with mutations that are strongly associated with neurodevelopmental disorders (NDD). Patients with PAK1 variants clinically present with intellectual disability, developmental delay, macrocephaly, and seizures. A targeted therapy currently does not exist for PAK1-associated intellectual disability. PAK1 is highly expressed in the brain throughout neurodevelopment, where IT regulates cortical development by promoting neural progenitor cell proliferation and neuronal migration. Normally, PAK1 exists in cells in an autoinhibited state, but upon binding of RHO-gtpases CDC42 or RAC1, PAK1 is activated. PAK1 is known to regulate cytoskeletal organization in neuronal development with constitutively active PAK1 increasing primary dendrites and altering dendritic spines morphology. Although PAK1 is known to be essential for neuronal development, the molecular mechanisms underlying its neuronal function are unknown largely because downstream phosphorylation targets of PAK1 have not yet been identified. I have demonstrated that NDD-associated PAK1 mutations increase its catalytic activity, but the impact of this overactivation on neurodevelopment has not been explored. Investigation of these two distinct but complementary aspects of PAK1 function will further our understanding of how this kinase regulates neuronal development, and how its dysfunction contributes to human neurodevelopmental disorder. The central hypothesis of this proposal is that PAK1 regulates neuronal development through phosphorylation of key downstream substrates and that overactivation of these signaling pathways caused by NDD-associated PAK1 mutations contributes to neuropathology. In aim 1, I will investigate the role of PAK1 in neurodevelopmental disorder by elucidating how overactive NDD-associated mutations affect neuronal development using primary cortical neuron cultures (aim 1A) and how these variants disrupt PAK1 autoinhibition through octet biolayer interferometry (aim 1B). By utilizing a chemical genetic approach with an engineered human PAK1 ATP-analog- sensitive kinase, I have identified 98 candidate PAK1 substrates in mouse brain lysate. In aim 2, I will determine which of these candidates are direct phosphorylation targets of PAK1 through biochemical validation (aim 2A) and characterize the role of these substrates in neuronal development (aim 2B). Successful completion of this proposal will elucidate the molecular function of PAK1 in both normal neuronal development and disease states and will have translational value for neurodevelopmental disorders. Completion of aim 1 will provide training in the use of biophysical techniques such as octet BLI, protein purification, computational modeling, primary neuronal culture, and neuronal morphology analysis. Completion of aim 2 will provide valuable training in chemical genetics, biochemical kinase assays, super-resolution SIM microscopy, advanced image analysis techniques, and phosphoproteomic data analyses.