Vascular proliferative diseases are characterized by VSMC proliferation and migration. Kinase interacting with stathmin (KIS) targets 2 key regulators of cell proliferation and migration, the cyclin-dependent kinase inhibitor p27Kip1 and the microtubule-destabilizing protein stathmin. Phosphorylation of p27Kip1 by KIS leads to cell-cycle progression, whereas the target sequence and the physiological relevance of KIS-mediated stathmin phosphorylation in VSMCs are unknown. Here we demonstrated that vascular wound repair in KIS–/– mice resulted in accelerated formation of neointima, which is composed predominantly of VSMCs. Deletion of KIS increased VSMC migratory activity and cytoplasmic tubulin destabilizing activity, but abolished VSMC proliferation through the delayed nuclear export and degradation of p27Kip1. This promigratory phenotype resulted from increased stathmin protein levels, caused by a lack of KIS-mediated stathmin phosphorylation at serine 38 and diminished stathmin protein degradation. Downregulation of stathmin in KIS–/– VSMCs fully restored the phenotype, and stathmin-deficient mice demonstrated reduced lesion formation in response to vascular injury. These data suggest that KIS protects against excessive neointima formation by opposing stathmin-mediated VSMC migration and that VSMC migration represents a major mechanism of vascular wound repair, constituting a relevant target and mechanism for therapeutic interventions.
Thomas H. Langenickel, Michelle Olive, Manfred Boehm, Hong San, Martin F. Crook, Elizabeth G. Nabel