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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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Inhibition of plus-end directed transport of mitochondria by tau, MAP2c, and MAP4. (a) Untransfected CHO control cells stained for tubulin (green) and mitochondria (MitoTracker, red). Note that mitochondria are distributed throughout the cell. (b) CHO cell stably transfected with GFP-tau. (c) CHO cells stably transfected with MAP2c (HA-tagged, blue), (d) stained for tubulin (green) and mitochondria (red, yellow). (e) CHO cells stably transfected with MAP4-BD (HA tagged), (f) stained for tubulin and mitochondria. Note that all MAPs in b–e cause clustering of mitochondria at the MTOC.
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fig1: Inhibition of plus-end directed transport of mitochondria by tau, MAP2c, and MAP4. (a) Untransfected CHO control cells stained for tubulin (green) and mitochondria (MitoTracker, red). Note that mitochondria are distributed throughout the cell. (b) CHO cell stably transfected with GFP-tau. (c) CHO cells stably transfected with MAP2c (HA-tagged, blue), (d) stained for tubulin (green) and mitochondria (red, yellow). (e) CHO cells stably transfected with MAP4-BD (HA tagged), (f) stained for tubulin and mitochondria. Note that all MAPs in b–e cause clustering of mitochondria at the MTOC.

Mentions: MAPs are known as stabilizers of microtubules and promoters of neurite outgrowth. In the case of the neuronal tau protein another potential function is the regulation of intracellular traffic (Ebneth et al., 1998). This ability of tau appears to be rather general, it occurs in all cell types where tau is expressed, and it affects all cargoes transported along microtubules tested so far (vesicles, organelles, intermediate filaments, etc.). Because tau is a neuronal MAP it was of particular interest for neurodegeneration in Alzheimer's disease where traffic along microtubules is interrupted (Stamer et al., 2002). However, it was an open question whether other MAPs in other cell types could affect microtubule transport in a similar fashion. We addressed this issue by studying MAP2 and MAP4, two major types of MAPs. CHO cells were stably transfected with MAP2c (the juvenile short isoform of the neuronal MAP2) or MAP4-BD, the microtubule-binding domain of the ubiquitous MAP4 (Olson et al., 1995), and the transport of vesicles, mitochondria, peroxisomes, or vimentin intermediate filaments was monitored (Fig. 1). In each case one observes an inhibition of net outward transport which results in the clustering of the cargoes in the cell center. In wild-type cells, mitochondria are distributed throughout the cytoplasm (Fig. 1 a), but in stably MAP-transfected cells they congregate around the MTOC (Fig. 1, b, d, and f). This effect is reminiscent of that of tau and is explained by a general inhibition of motor proteins which affects kinesin more than dynein so that the centripetal movements dominate (Trinczek et al., 1999). The effect depends on the affinity and concentration of MAPs, i.e., low levels of MAPs or loosely bound MAP constructs have only little effect on traffic. Because the binding of MAPs to microtubules is regulated by phosphorylation one would expect that kinases that detach MAPs from microtubules would relieve the inhibition of motors. One kinase family that detaches tau, MAP2, and MAP4 efficiently from microtubules is MARK, which phosphorylates the KXGS motifs in the repeat domain of these MAPs (Illenberger et al., 1996). Thus, a major aim of this work was to find out whether kinases of the MARK family could indeed counteract the transport inhibition by MAPs.


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)

Inhibition of plus-end directed transport of mitochondria by tau, MAP2c, and MAP4. (a) Untransfected CHO control cells stained for tubulin (green) and mitochondria (MitoTracker, red). Note that mitochondria are distributed throughout the cell. (b) CHO cell stably transfected with GFP-tau. (c) CHO cells stably transfected with MAP2c (HA-tagged, blue), (d) stained for tubulin (green) and mitochondria (red, yellow). (e) CHO cells stably transfected with MAP4-BD (HA tagged), (f) stained for tubulin and mitochondria. Note that all MAPs in b–e cause clustering of mitochondria at the MTOC.
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Related In: Results  -  Collection

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

fig1: Inhibition of plus-end directed transport of mitochondria by tau, MAP2c, and MAP4. (a) Untransfected CHO control cells stained for tubulin (green) and mitochondria (MitoTracker, red). Note that mitochondria are distributed throughout the cell. (b) CHO cell stably transfected with GFP-tau. (c) CHO cells stably transfected with MAP2c (HA-tagged, blue), (d) stained for tubulin (green) and mitochondria (red, yellow). (e) CHO cells stably transfected with MAP4-BD (HA tagged), (f) stained for tubulin and mitochondria. Note that all MAPs in b–e cause clustering of mitochondria at the MTOC.
Mentions: MAPs are known as stabilizers of microtubules and promoters of neurite outgrowth. In the case of the neuronal tau protein another potential function is the regulation of intracellular traffic (Ebneth et al., 1998). This ability of tau appears to be rather general, it occurs in all cell types where tau is expressed, and it affects all cargoes transported along microtubules tested so far (vesicles, organelles, intermediate filaments, etc.). Because tau is a neuronal MAP it was of particular interest for neurodegeneration in Alzheimer's disease where traffic along microtubules is interrupted (Stamer et al., 2002). However, it was an open question whether other MAPs in other cell types could affect microtubule transport in a similar fashion. We addressed this issue by studying MAP2 and MAP4, two major types of MAPs. CHO cells were stably transfected with MAP2c (the juvenile short isoform of the neuronal MAP2) or MAP4-BD, the microtubule-binding domain of the ubiquitous MAP4 (Olson et al., 1995), and the transport of vesicles, mitochondria, peroxisomes, or vimentin intermediate filaments was monitored (Fig. 1). In each case one observes an inhibition of net outward transport which results in the clustering of the cargoes in the cell center. In wild-type cells, mitochondria are distributed throughout the cytoplasm (Fig. 1 a), but in stably MAP-transfected cells they congregate around the MTOC (Fig. 1, b, d, and f). This effect is reminiscent of that of tau and is explained by a general inhibition of motor proteins which affects kinesin more than dynein so that the centripetal movements dominate (Trinczek et al., 1999). The effect depends on the affinity and concentration of MAPs, i.e., low levels of MAPs or loosely bound MAP constructs have only little effect on traffic. Because the binding of MAPs to microtubules is regulated by phosphorylation one would expect that kinases that detach MAPs from microtubules would relieve the inhibition of motors. One kinase family that detaches tau, MAP2, and MAP4 efficiently from microtubules is MARK, which phosphorylates the KXGS motifs in the repeat domain of these MAPs (Illenberger et al., 1996). Thus, a major aim of this work was to find out whether kinases of the MARK family could indeed counteract the transport inhibition by MAPs.

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