Experimental studies in flies, mice, and humans suggest a significant role of impaired axonal transport in the pathogenesis of Alzheimer's disease (AD). The mechanisms underlying these impairments in axonal transport, however, remain poorly understood. Here we report that the Swedish familial AD mutation causes a standstill of the amyloid precursor protein (APP) in the axons at the expense of its reduced anterograde transport. The standstill reflects the perturbed directionality of the axonal transport of APP, which spends significantly more time traveling in the retrograde direction. This ineffective movement is accompanied by an enhanced association of dynactin-1 with APP, which suggests that reduced anterograde transport of APP is the result of enhanced activation of the retrograde molecular motor dynein by dynactin-1. The impact of the Swedish mutation on axonal transport is not limited to the APP vesicles since it also reverses the directionality of a subset of early endosomes, which become enlarged and aberrantly accumulate in distal locations. In addition, it also reduces the trafficking of lysosomes due to their less effective retrograde movement. Altogether, our experiments suggest a pivotal involvement of retrograde molecular motors and transport in the mechanisms underlying impaired axonal transport in AD and reveal significantly more widespread derangement of axonal transport pathways in the pathogenesis of AD.
- MeSH
- Alzheimerova nemoc * metabolismus genetika patologie MeSH
- amyloidový prekurzorový protein beta * genetika metabolismus MeSH
- axonální transport * genetika MeSH
- axony metabolismus patologie MeSH
- dynaktinový komplex metabolismus genetika MeSH
- dyneiny metabolismus MeSH
- endozomy metabolismus genetika MeSH
- genetická variace MeSH
- lidé MeSH
- lyzozomy metabolismus MeSH
- mutace MeSH
- myši MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Amyotrophic lateral sclerosis (ALS) is a fatal non-cell-autonomous neurodegenerative disease characterized by the loss of motor neurons (MNs). Mutations in CRMP4 are associated with ALS in patients, and elevated levels of CRMP4 are suggested to affect MN health in the SOD1G93A -ALS mouse model. However, the mechanism by which CRMP4 mediates toxicity in ALS MNs is poorly understood. Here, by using tissue from human patients with sporadic ALS, MNs derived from C9orf72-mutant patients, and the SOD1G93A -ALS mouse model, we demonstrate that subcellular changes in CRMP4 levels promote MN loss in ALS. First, we show that while expression of CRMP4 protein is increased in cell bodies of ALS-affected MN, CRMP4 levels are decreased in the distal axons. Cellular mislocalization of CRMP4 is caused by increased interaction with the retrograde motor protein, dynein, which mediates CRMP4 transport from distal axons to the soma and thereby promotes MN loss. Blocking the CRMP4-dynein interaction reduces MN loss in human-derived MNs (C9orf72) and in ALS model mice. Thus, we demonstrate a novel CRMP4-dependent retrograde death signal that underlies MN loss in ALS.
- MeSH
- amyotrofická laterální skleróza genetika metabolismus MeSH
- axonální transport * MeSH
- axony metabolismus MeSH
- buněčná smrt MeSH
- buněčné linie MeSH
- dyneiny metabolismus MeSH
- kultivované buňky MeSH
- motorické neurony metabolismus patologie MeSH
- myši inbrední C57BL MeSH
- myši MeSH
- proteiny nervové tkáně genetika metabolismus MeSH
- signální transdukce MeSH
- superoxiddismutasa 1 genetika MeSH
- zvířata MeSH
- Check Tag
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
The maintenance of intracellular processes, like organelle transport and cell division, depend on bidirectional movement along microtubules. These processes typically require kinesin and dynein motor proteins, which move with opposite directionality. Because both types of motors are often simultaneously bound to the cargo, regulatory mechanisms are required to ensure controlled directional transport. Recently, it has been shown that parameters like mechanical motor activation, ATP concentration and roadblocks on the microtubule surface differentially influence the activity of kinesin and dynein motors in distinct manners. However, how these parameters affect bidirectional transport systems has not been studied. Here, we investigate the regulatory influence of these three parameters using in vitro gliding motility assays and stochastic simulations. We find that the number of active kinesin and dynein motors determines the transport direction and velocity, but that variations in ATP concentration and roadblock density have no significant effect. Thus, factors influencing the force balance between opposite motors appear to be important, whereas the detailed stepping kinetics and bypassing capabilities of the motors only have a small effect.
The transcription factor ASCIZ (ATMIN, ZNF822) has an unusually high number of recognition motifs for the product of its main target gene, the hub protein LC8 (DYNLL1). Using a combination of biophysical methods, structural analysis by NMR and electron microscopy, and cellular transcription assays, we developed a model that proposes a concerted role of intrinsic disorder and multiple LC8 binding events in regulating LC8 transcription. We demonstrate that the long intrinsically disordered C-terminal domain of ASCIZ binds LC8 to form a dynamic ensemble of complexes with a gradient of transcriptional activity that is inversely proportional to LC8 occupancy. The preference for low occupancy complexes at saturating LC8 concentrations with both human and Drosophila ASCIZ indicates that negative cooperativity is an important feature of ASCIZ-LC8 interactions. The prevalence of intrinsic disorder and multivalency among transcription factors suggests that formation of heterogeneous, dynamic complexes is a widespread mechanism for tuning transcriptional regulation.
- MeSH
- cytoplazmatické dyneiny chemie genetika metabolismus MeSH
- Drosophila melanogaster růst a vývoj metabolismus fyziologie MeSH
- dyneiny chemie genetika metabolismus MeSH
- lidé MeSH
- proteiny Drosophily chemie genetika metabolismus MeSH
- regulace genové exprese * MeSH
- transkripční faktory chemie genetika metabolismus MeSH
- vnitřně neuspořádané proteiny genetika metabolismus MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
Despite extensive data demonstrating that immature retroviral particle assembly can take place either at the plasma membrane or at a distinct location within the cytoplasm, targeting of viral precursor proteins to either assembly site still remains poorly understood. Biochemical data presented here suggest that Tctex-1, a light chain of the molecular motor dynein, is involved in the intracellular targeting of Mason-Pfizer monkey virus (M-PMV) polyproteins to the cytoplasmic assembly site. Comparison of the three-dimensional structures of M-PMV wild-type matrix protein (wt MA) with a single amino acid mutant (R55F), which redirects assembly from a cytoplasmic site to the plasma membrane, revealed different mutual orientations of their C- and N-terminal domains. This conformational change buries a putative intracellular targeting motif located between both domains in the hydrophobic pocket of the MA molecule, thereby preventing the interaction with cellular transport mechanisms.
- MeSH
- biologické modely MeSH
- biologický transport MeSH
- buněčná membrána metabolismus virologie MeSH
- Cercopithecus aethiops MeSH
- COS buňky MeSH
- cytoplazma metabolismus MeSH
- dyneiny metabolismus MeSH
- fenotyp MeSH
- financování organizované MeSH
- genomová oblast t-komplexu MeSH
- jaderné proteiny fyziologie chemie metabolismus MeSH
- lidé MeSH
- Masonův-Pfizerův opičí virus metabolismus MeSH
- mutace MeSH
- proteiny asociované s mikrotubuly fyziologie chemie metabolismus MeSH
- Retroviridae metabolismus MeSH
- terciární struktura proteinů MeSH
- vazebná místa MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
