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MARK/PAR1 kinase is a regulator of microtubule-dependent transport in axons.

Mandelkow EM, Thies E, Trinczek B, Biernat J, Mandelkow E - J. Cell Biol. (2004)

Bottom Line: The transport can be regulated through motor proteins, cargo adaptors, or microtubule tracks.This occurs without impairing the intrinsic activity of motors because the velocity during active movement remains unchanged.This transport inhibition can be rescued by phosphorylating tau with MARK.

View Article: PubMed Central - PubMed

Affiliation: Max-Planck Unit for Structural Molecular Biology, 22607 Hamburg, Germany. mandelkow@mpasmb.desy.de

ABSTRACT
Microtubule-dependent transport of vesicles and organelles appears saltatory because particles switch between periods of rest, random Brownian motion, and active transport. The transport can be regulated through motor proteins, cargo adaptors, or microtubule tracks. We report here a mechanism whereby microtubule associated proteins (MAPs) represent obstacles to motors which can be regulated by microtubule affinity regulating kinase (MARK)/Par-1, a family of kinases that is known for its involvement in establishing cell polarity and in phosphorylating tau protein during Alzheimer neurodegeneration. Expression of MARK causes the phosphorylation of MAPs at their KXGS motifs, thereby detaching MAPs from the microtubules and thus facilitating the transport of particles. This occurs without impairing the intrinsic activity of motors because the velocity during active movement remains unchanged. In primary retinal ganglion cells, transfection with tau leads to the inhibition of axonal transport of mitochondria, APP vesicles, and other cell components which leads to starvation of axons and vulnerability against stress. This transport inhibition can be rescued by phosphorylating tau with MARK.

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Distributions of mitochondria in RGC axons, 48 h after transfection with Tau by adenovirus. (a–c) Field of axons stained with MitoTracker (a), CFP-Tau (b), and merge (c). Mitochondria are frequent in normal axons, but have almost disappeared from tau-transfected axons (see bottom axon in b and c, blue, closed arrowheads). (d–f) Expression of tau with time after transfection, and (g–i) corresponding clustering of mitochondria in cell body. Tau gradually moves out into the axon, whereas mitochondria accumulate in the cell body. (j and k) Quantification of mitochondria movements in controls (j) and tau-transfected cells (k). In control cells, anterograde movements dominate (55%, dark blue bar), in tau-transfected cells anterograde transport decreases (to 7%), immobile particles increase (to 50%, red bar), and retrogradely moving particles increase (to 45%, light blue bar). Error bars indicate SEM.
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fig5: Distributions of mitochondria in RGC axons, 48 h after transfection with Tau by adenovirus. (a–c) Field of axons stained with MitoTracker (a), CFP-Tau (b), and merge (c). Mitochondria are frequent in normal axons, but have almost disappeared from tau-transfected axons (see bottom axon in b and c, blue, closed arrowheads). (d–f) Expression of tau with time after transfection, and (g–i) corresponding clustering of mitochondria in cell body. Tau gradually moves out into the axon, whereas mitochondria accumulate in the cell body. (j and k) Quantification of mitochondria movements in controls (j) and tau-transfected cells (k). In control cells, anterograde movements dominate (55%, dark blue bar), in tau-transfected cells anterograde transport decreases (to 7%), immobile particles increase (to 50%, red bar), and retrogradely moving particles increase (to 45%, light blue bar). Error bars indicate SEM.

Mentions: One aim of the experiments is to demonstrate the correlation between MARK activity, tau phosphorylation, and organelle movements in the same cell. In the RGC axons of Fig. 5 mitochondria show a roughly uniform distribution with a density around 0.17 particles/μm (Fig. 5 a). Most of these (55%) move anterogradely while the growth cone is advancing; smaller fractions move retrogradely (∼26%) or are stationary during the period of observation (24 min; Fig. 5 j). When these cells are transfected with CFP-tau the characteristics of movement change dramatically: over the time of 24 h, most mitochondria leave the axon and accumulate in the cell body because the dynein-mediated retrograde traffic dominates (Fig. 5, d–i). The density of mitochondria in the axons decreases strongly (0.08 particles/μm after 24 h; Fig. 5 c, arrow), the fraction of anterograde movements drops below 10%, and stationary or retrograde particles increase to nearly 50% (Fig. 5 k). This feature corresponds to the clustering of mitochondria in the cell body around the MTOC for CHO or N2a cells (Fig. 1, b, d, and f), and analogous observations apply to other cell organelles (e.g., lysosomes, peroxisomes) or transport vesicles (e.g., APP-containing vesicles; Stamer et al., 2002). Note that in spite of the retrograde flow of mitochondria, the expressed tau can move forward and fills the axon homogeneously, illustrating that the transport of tau (which is part of slow axonal transport; Mercken et al., 1995) differs from the fast axonal transport of vesicles and organelles.


MARK/PAR1 kinase is a regulator of microtubule-dependent transport in axons.

Mandelkow EM, Thies E, Trinczek B, Biernat J, Mandelkow E - J. Cell Biol. (2004)

Distributions of mitochondria in RGC axons, 48 h after transfection with Tau by adenovirus. (a–c) Field of axons stained with MitoTracker (a), CFP-Tau (b), and merge (c). Mitochondria are frequent in normal axons, but have almost disappeared from tau-transfected axons (see bottom axon in b and c, blue, closed arrowheads). (d–f) Expression of tau with time after transfection, and (g–i) corresponding clustering of mitochondria in cell body. Tau gradually moves out into the axon, whereas mitochondria accumulate in the cell body. (j and k) Quantification of mitochondria movements in controls (j) and tau-transfected cells (k). In control cells, anterograde movements dominate (55%, dark blue bar), in tau-transfected cells anterograde transport decreases (to 7%), immobile particles increase (to 50%, red bar), and retrogradely moving particles increase (to 45%, light blue bar). Error bars indicate SEM.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2172520&req=5

fig5: Distributions of mitochondria in RGC axons, 48 h after transfection with Tau by adenovirus. (a–c) Field of axons stained with MitoTracker (a), CFP-Tau (b), and merge (c). Mitochondria are frequent in normal axons, but have almost disappeared from tau-transfected axons (see bottom axon in b and c, blue, closed arrowheads). (d–f) Expression of tau with time after transfection, and (g–i) corresponding clustering of mitochondria in cell body. Tau gradually moves out into the axon, whereas mitochondria accumulate in the cell body. (j and k) Quantification of mitochondria movements in controls (j) and tau-transfected cells (k). In control cells, anterograde movements dominate (55%, dark blue bar), in tau-transfected cells anterograde transport decreases (to 7%), immobile particles increase (to 50%, red bar), and retrogradely moving particles increase (to 45%, light blue bar). Error bars indicate SEM.
Mentions: One aim of the experiments is to demonstrate the correlation between MARK activity, tau phosphorylation, and organelle movements in the same cell. In the RGC axons of Fig. 5 mitochondria show a roughly uniform distribution with a density around 0.17 particles/μm (Fig. 5 a). Most of these (55%) move anterogradely while the growth cone is advancing; smaller fractions move retrogradely (∼26%) or are stationary during the period of observation (24 min; Fig. 5 j). When these cells are transfected with CFP-tau the characteristics of movement change dramatically: over the time of 24 h, most mitochondria leave the axon and accumulate in the cell body because the dynein-mediated retrograde traffic dominates (Fig. 5, d–i). The density of mitochondria in the axons decreases strongly (0.08 particles/μm after 24 h; Fig. 5 c, arrow), the fraction of anterograde movements drops below 10%, and stationary or retrograde particles increase to nearly 50% (Fig. 5 k). This feature corresponds to the clustering of mitochondria in the cell body around the MTOC for CHO or N2a cells (Fig. 1, b, d, and f), and analogous observations apply to other cell organelles (e.g., lysosomes, peroxisomes) or transport vesicles (e.g., APP-containing vesicles; Stamer et al., 2002). Note that in spite of the retrograde flow of mitochondria, the expressed tau can move forward and fills the axon homogeneously, illustrating that the transport of tau (which is part of slow axonal transport; Mercken et al., 1995) differs from the fast axonal transport of vesicles and organelles.

Bottom Line: The transport can be regulated through motor proteins, cargo adaptors, or microtubule tracks.This occurs without impairing the intrinsic activity of motors because the velocity during active movement remains unchanged.This transport inhibition can be rescued by phosphorylating tau with MARK.

View Article: PubMed Central - PubMed

Affiliation: Max-Planck Unit for Structural Molecular Biology, 22607 Hamburg, Germany. mandelkow@mpasmb.desy.de

ABSTRACT
Microtubule-dependent transport of vesicles and organelles appears saltatory because particles switch between periods of rest, random Brownian motion, and active transport. The transport can be regulated through motor proteins, cargo adaptors, or microtubule tracks. We report here a mechanism whereby microtubule associated proteins (MAPs) represent obstacles to motors which can be regulated by microtubule affinity regulating kinase (MARK)/Par-1, a family of kinases that is known for its involvement in establishing cell polarity and in phosphorylating tau protein during Alzheimer neurodegeneration. Expression of MARK causes the phosphorylation of MAPs at their KXGS motifs, thereby detaching MAPs from the microtubules and thus facilitating the transport of particles. This occurs without impairing the intrinsic activity of motors because the velocity during active movement remains unchanged. In primary retinal ganglion cells, transfection with tau leads to the inhibition of axonal transport of mitochondria, APP vesicles, and other cell components which leads to starvation of axons and vulnerability against stress. This transport inhibition can be rescued by phosphorylating tau with MARK.

Show MeSH
Related in: MedlinePlus