CDK5‐dependent activation of dynein in the axon initial segment regulates polarized cargo transport in neurons. (8th November 2017)

• Record Type: Journal Article
• Authors: Klinman, Eva; Tokito, Mariko; Holzbaur, Erika L. F.
• Is Part Of: Traffic. Volume 18:Number 12(2017)
• Page Start: 808
• Page End: 824
• Publication Date: 2017-11-08
• Subjects: axon initial segment -- CDK5 -- dynein -- Lis1 -- microtubule polarity -- Ndel1 -- polarized transport; Biological transport -- Periodicals; 571.6
• DOI: 10.1111/tra.12529
• Languages: English
• ISSNs: 1398-9219

Abstract

Abstract : Klinman et al demonstrate evidence of localized dynein activation at the axon initial segment (AIS), and show that upstream cyclin‐dependent kinase 5 (CDK5) activation is required to maintain the normal organization of the AIS and its role as a cargo filter. They determine that disruption of the CDK5‐Ndel1‐Lis1‐dynein mechanism results in aberrant permeability of the AIS to dendritic cargo and changes in axonal microtubule polarity, in a time‐dependent fashion. These findings indicate an essential homeostatic function for dynein and CDK5 in controlling AIS integrity. Abstract : The unique polarization of neurons depends on selective sorting of axonal and somatodendritic cargos to their correct compartments. Axodendritic sorting and filtering occurs within the axon initial segment (AIS). However, the underlying molecular mechanisms responsible for this filter are not well understood. Here, we show that local activation of the neuronal‐specific kinase cyclin‐dependent kinase 5 (CDK5) is required to maintain AIS integrity, as depletion or inhibition of CDK5 induces disordered microtubule polarity and loss of AIS cytoskeletal structure. Furthermore, CDK5‐dependent phosphorylation of the dynein regulator Ndel1 is required for proper re‐routing of mislocalized somatodendritic cargo out of the AIS; inhibition of this pathway induces profound mis‐sorting defects. While inhibition of the CDK5‐Ndel1‐Lis1‐dynein pathway alters both axonal microtubule polarity and axodendritic sorting, we found that these defects occur on distinct timescales; brief inhibition of dynein disrupts axonal cargo sorting before loss of microtubule polarity becomes evident. Together, these studies identify CDK5 as a master upstream regulator of trafficking in vertebrate neurons, required for both AIS microtubule organization and polarized dynein‐dependent sorting of axodendritic cargos, and support an ongoing and essential role for dynein at the AIS.