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Dynein intermediate chain mediated dynein-dynactin interaction is required for interphase microtubule organization and centrosome replication and separation in Dictyostelium.

Ma S, Triviños-Lagos L, Gräf R, Chisholm RL - J. Cell Biol. (1999)

Bottom Line: Biol.ICDeltaC associated with dynactin but not with dynein heavy chain, whereas ICDeltaN truncations bound to dynein but bound dynactin poorly.Both mutations resulted in abnormal localization to the Golgi complex, confirming dynein function was disrupted.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell and Molecular Biology, Robert H. Lurie Comprehensive Cancer Center, Northwestern University Medical School, Chicago, Illinois 60611, USA.

ABSTRACT
Cytoplasmic dynein intermediate chain (IC) mediates dynein-dynactin interaction in vitro (Karki, S., and E.L. Holzbaur. 1995. J. Biol. Chem. 270:28806-28811; Vaughan, K.T., and R.B. Vallee. 1995. J. Cell Biol. 131:1507-1516). To investigate the physiological role of IC and dynein-dynactin interaction, we expressed IC truncations in wild-type Dictyostelium cells. ICDeltaC associated with dynactin but not with dynein heavy chain, whereas ICDeltaN truncations bound to dynein but bound dynactin poorly. Both mutations resulted in abnormal localization to the Golgi complex, confirming dynein function was disrupted. Striking disorganization of interphase microtubule (MT) networks was observed when mutant expression was induced. In a majority of cells, the MT networks collapsed into large bundles. We also observed cells with multiple cytoplasmic asters and MTs lacking an organizing center. These cells accumulated abnormal DNA content, suggesting a defect in mitosis. Striking defects in centrosome morphology were also observed in IC mutants, mostly larger than normal centrosomes. Ultrastructural analysis of centrosomes in IC mutants showed interphase accumulation of large centrosomes typical of prophase as well as unusually paired centrosomes, suggesting defects in centrosome replication and separation. These results suggest that dynactin-mediated cytoplasmic dynein function is required for the proper organization of interphase MT network as well as centrosome replication and separation in Dictyostelium.

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Model for the role of dynein in interphase MT organization and mitotic centrosome separation. Also shown is the mechanism by which IC truncation mutants might disrupt dynein function. N, nucleus; C, cytoplasm; V, membranous vesicles. Arrows indicate the direction of force applied on MTs by dynein. +/− depicts the ends of MTs. See Discussion for details.
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Figure 11: Model for the role of dynein in interphase MT organization and mitotic centrosome separation. Also shown is the mechanism by which IC truncation mutants might disrupt dynein function. N, nucleus; C, cytoplasm; V, membranous vesicles. Arrows indicate the direction of force applied on MTs by dynein. +/− depicts the ends of MTs. See Discussion for details.

Mentions: In sum, our results, together with the work of others, suggests the model shown in Fig. 11 for the role of dynein in MT organization and centrosome separation. Dynein, acting through an association with dynactin, could produce traction forces acting either along the sides or on the plus-ends of cytoplasmic MTs to maintain the radial array or direct the movement of the MT network in interphase. During mitosis, the pulling force on astral MTs could facilitate centrosome replication and spindle pole separation. Cytoplasmic dynein might exert such plus-end–directed forces on MTs and centrosomes by anchoring on membranous organelles, including the nuclear membrane or cell cortex. This anchoring of cytoplasmic dynein is dependent on its proper association with dynactin. The IC serves as a bridge between cytoplasmic dynein and dynactin complex and is crucial for their interaction. Overexpression of IC truncation mutants disrupts the binding of cytoplasmic dynein to dynactin, leading to dissociation of dynein from its cytoplasmic anchoring points. Without anchoring points, dynein could no longer produce tension on MTs, resulting in collapsed MT arrays and abolished centrosome separation.


Dynein intermediate chain mediated dynein-dynactin interaction is required for interphase microtubule organization and centrosome replication and separation in Dictyostelium.

Ma S, Triviños-Lagos L, Gräf R, Chisholm RL - J. Cell Biol. (1999)

Model for the role of dynein in interphase MT organization and mitotic centrosome separation. Also shown is the mechanism by which IC truncation mutants might disrupt dynein function. N, nucleus; C, cytoplasm; V, membranous vesicles. Arrows indicate the direction of force applied on MTs by dynein. +/− depicts the ends of MTs. See Discussion for details.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2168085&req=5

Figure 11: Model for the role of dynein in interphase MT organization and mitotic centrosome separation. Also shown is the mechanism by which IC truncation mutants might disrupt dynein function. N, nucleus; C, cytoplasm; V, membranous vesicles. Arrows indicate the direction of force applied on MTs by dynein. +/− depicts the ends of MTs. See Discussion for details.
Mentions: In sum, our results, together with the work of others, suggests the model shown in Fig. 11 for the role of dynein in MT organization and centrosome separation. Dynein, acting through an association with dynactin, could produce traction forces acting either along the sides or on the plus-ends of cytoplasmic MTs to maintain the radial array or direct the movement of the MT network in interphase. During mitosis, the pulling force on astral MTs could facilitate centrosome replication and spindle pole separation. Cytoplasmic dynein might exert such plus-end–directed forces on MTs and centrosomes by anchoring on membranous organelles, including the nuclear membrane or cell cortex. This anchoring of cytoplasmic dynein is dependent on its proper association with dynactin. The IC serves as a bridge between cytoplasmic dynein and dynactin complex and is crucial for their interaction. Overexpression of IC truncation mutants disrupts the binding of cytoplasmic dynein to dynactin, leading to dissociation of dynein from its cytoplasmic anchoring points. Without anchoring points, dynein could no longer produce tension on MTs, resulting in collapsed MT arrays and abolished centrosome separation.

Bottom Line: Biol.ICDeltaC associated with dynactin but not with dynein heavy chain, whereas ICDeltaN truncations bound to dynein but bound dynactin poorly.Both mutations resulted in abnormal localization to the Golgi complex, confirming dynein function was disrupted.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell and Molecular Biology, Robert H. Lurie Comprehensive Cancer Center, Northwestern University Medical School, Chicago, Illinois 60611, USA.

ABSTRACT
Cytoplasmic dynein intermediate chain (IC) mediates dynein-dynactin interaction in vitro (Karki, S., and E.L. Holzbaur. 1995. J. Biol. Chem. 270:28806-28811; Vaughan, K.T., and R.B. Vallee. 1995. J. Cell Biol. 131:1507-1516). To investigate the physiological role of IC and dynein-dynactin interaction, we expressed IC truncations in wild-type Dictyostelium cells. ICDeltaC associated with dynactin but not with dynein heavy chain, whereas ICDeltaN truncations bound to dynein but bound dynactin poorly. Both mutations resulted in abnormal localization to the Golgi complex, confirming dynein function was disrupted. Striking disorganization of interphase microtubule (MT) networks was observed when mutant expression was induced. In a majority of cells, the MT networks collapsed into large bundles. We also observed cells with multiple cytoplasmic asters and MTs lacking an organizing center. These cells accumulated abnormal DNA content, suggesting a defect in mitosis. Striking defects in centrosome morphology were also observed in IC mutants, mostly larger than normal centrosomes. Ultrastructural analysis of centrosomes in IC mutants showed interphase accumulation of large centrosomes typical of prophase as well as unusually paired centrosomes, suggesting defects in centrosome replication and separation. These results suggest that dynactin-mediated cytoplasmic dynein function is required for the proper organization of interphase MT network as well as centrosome replication and separation in Dictyostelium.

Show MeSH
Related in: MedlinePlus