title: The p21-activated kinase PAK3 forms heterodimers with PAK1 in brain implementing trans-regulation of PAK3 activity.
abstract: p21-activated kinase 1 (PAK1) and PAK3 belong to group I of the PAK family and control cell movement and division. They also regulate dendritic spine formation and maturation in the brain, and play a role in synaptic transmission and synaptic plasticity. PAK3, in particular, is known for its implication in X-linked intellectual disability. The pak3 gene is expressed in neurons as a GTPase-regulated PAK3a protein and also as three splice variants which display constitutive kinase activity. PAK1 regulation is based on its homodimerization, forming an inactive complex. Here, we analyze the PAK3 capacity to dimerize and show that although PAK3a is able to homodimerize, it is more likely to form heterodimeric complexes with PAK1. We further show that two intellectual disability mutations impair dimerization with PAK1. The b and c inserts present in the regulatory domain of PAK3 splice variants decrease the dimerization but retain the capacity to form heterodimers with PAK1. PAK1 and PAK3 are co-expressed in neurons, are colocalized within dendritic spines, co-purify with post-synaptic densities, and co-immunoprecipitate in brain lysates. Using kinase assays, we demonstrate that PAK1 inhibits the activity of PAK3a but not of the splice variant PAK3b in a trans-regulatory manner. Altogether, these results show that PAK3 and PAK1 signaling may be coordinated by heterodimerization.
authors: Centre de Neurosciences Paris-Sud, Université Paris-Sud, UMR 8195 and CNRS, UMR 8195, Orsay F-91405, France.
authors: Gaëlle
authors: G
authors: Combeau
authors: Patricia
authors: P
authors: Kreis
authors: Florence
authors: F
authors: Domenichini
authors: Muriel
authors: M
authors: Amar
authors: Philippe
authors: P
authors: Fossier
authors: Véronique
authors: V
authors: Rousseau
authors: Jean-Vianney
authors: JV
authors: Barnier
mesh_terms: D017398:Alternative Splicing / Q000235:genetics; D000818:Animals; D049229:Dendritic Spines / Q000201:enzymology*; D004789:Enzyme Activation / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics; D040181:Genetic Diseases, X-Linked / Q000201:enzymology / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D008607:Intellectual Disability / Q000201:enzymology / Q000235:genetics; D051379:Mice; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D057907:Post-Synaptic Density / Q000201:enzymology*; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D015398:Signal Transduction / Q000235:genetics; D054462:p21-Activated Kinases / Q000235:genetics / Q000378:metabolism*
chemical_list: D009419:Nerve Tissue Proteins; C515905:Pak1 protein, mouse; C515912:Pak3 protein, mouse; D054462:p21-Activated Kinases