Analysis of Tau phosphorylation in kinesin Kif21b-depleted neurons and kinesin-dependent cargo transport under inflammatory conditions

Abstract

The first part investigates KIF21B, a member of the kinesin superfamily of proteins that have been implicated in the pathogenesis of Alzheimer's disease, a progressive neurodegenerative disorder marked by the presence of extracellular amyloid β plaques and intracellular Tau neurofibrillary tangles. The phosphorylation status of Tau, a microtubule-associated protein, is regulated by the Akt/GSK3β signaling pathway. KIF21B has been reported to modulate osteosarcoma cell proliferation and apoptosis through the PI3K/Akt pathway. Therefore, there is a hypothesis that KIF21B may affect PI3K/Akt pathway in hippocampal neurons and, consequently, Tau phosphorylation. Western blot analysis and immunohistochemistry performed on KIF21B knockout mice showed reduced levels of phosphorylated Akt (pAkt), raised phosphorylated GSK3β (Tyr216), and increased Tau phosphorylation, thus supporting a signaling pathway linking KIF21B to the pathogenesis of Alzheimer's disease.

The second part explores multiple sclerosis, a common neuroinflammatory disease characterized by progressive axonal degeneration. Extensive transport impairments and reduced distal organelles supply may contribute to the disease's chronic axonal atrophy. Genetic variations in the Kif21b gene have been associated with multiple sclerosis. However, the specific motors affected at the onset of inflammation remain poorly understood. The first step was to build a wild-type initial model of neuroinflammation. Here, mouse cortical neurons were subjected at the day in vitro (DIV) 12 to a 48-hour inflammatory cocktail (IC) containing IFN-γ, TNF-α, IL17 (each at 100nM), or control conditions. Live-cell imaging studies of bidirectional axonal transport of kinesin-dependent synaptophysin, BDNF, N-cadherin, and dynein-dependent LAMP1 proteins were conducted. Results showed no significant differences in average transport velocities, suggesting that initial inflammatory stimuli do not immediately affect transport.