Centrosomal JAK2 Tyrosine Kinase Regulates Primary Cilia Length, Cell Proliferation, and Cilia Orientation During Cell Migration.

Janus kinase 2 (JAK2) is best known for its role in cytokine signaling at the plasma membrane, but whether it contributes to primary cilium function is unknown. Here we show that JAK2 localizes predominantly to the daughter centriole of the primary cilium in 3T3-F442A fibroblasts and regulates cilia length and orientation as well as directional cell migration. Growth hormone (GH) stimulates relocation of growth hormone receptor to the cilium and shortens cilia, whereas pharmacological JAK2 inhibition or CRISPR-mediated JAK2 knockout (KO) results in cilia elongation. Using a nocodazole washout assay, we find that JAK2 activity is required for proper control of cilia length during cilia re-assembly. Centrosomal localization of JAK2 depends on both its SH2 domain and kinase activity, and JAK2 clones deficient in centrosomal targeting or kinase function demonstrate impaired control of cilia length and reduced cell proliferation compared with parental and JAK2 WT cells. Depletion of centrosomes by centrinone B or loss of centrosomal JAK2 impairs wound-healing migration and disrupts alignment of primary cilia toward the direction of movement. JAK2 copurifies with the actin-regulating proteins PAK1 and Filamin A in centrosomal fractions, and JAK2 activity is required for Filamin A centrosomal association. Together, our data identify centrosomal JAK2 as a critical regulator of primary cilia architecture and orientation during cell migration, supporting a model in which a JAK2-PAK1-Filamin A signaling complex contributes to cilia-dependent control of cell motility and cell proliferation and suggests new mechanisms by which cytokine signaling interfaces with cilia-dependent cell behavior.