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M phase phosphoprotein 1 is a human plus-end-directed kinesin-related protein required for cytokinesis
Aouatef Abaza1, Jean-Marc Soleilhac, Joanne Westendorf
1INSERM U366, Département Réponse et Dynamique Cellulaires, Laboratoire du Cytosquelette, Commissariat à l'Energie Atomique-Grenoble, 17 rue des Martyrs, 38 054 Grenoble Cedex 9, France.
Abstract:
The human M phase phosphoprotein 1 (MPP1), previously identified through a screening of a subset of proteins specifically phosphorylated at the G2/M transition (Matsumoto-Taniura, N., Pirollet, F., Monroe, R., Gerace, L., and Westendorf, J. M. (1996) Mol. Biol. Cell 7, 1455-1469), is characterized as a plus-end-directed kinesin-related protein. Recombinant MPP1 exhibits in vitro microtubule-binding and microtubule-bundling properties as well as microtubule-stimulated ATPase activity. In gliding experiments using polarity-marked microtubules, MPP1 is a slow molecular motor that moves toward the microtubule plus-end at a 0.07 microm/s speed. In cycling cells, MPP1 localizes mainly to the nuclei in interphase. During mitosis, MPP1 is diffuse throughout the cytoplasm in metaphase and subsequently localizes to the midzone to further concentrate on the midbody. MPP1 suppression by RNA interference induces failure of cell division late in cytokinesis. We conclude that MPP1 is a new mitotic molecular motor required for completion of cytokinesis.
Insights
Human M phase phosphoprotein 1 (MPP1) functions as a molecular motor crucial for cell division. MPP1 is essential for the successful completion of cytokinesis, ensuring proper cell separation during mitosis.
Area of Science:
- Cell Biology
- Molecular Motor Proteins
- Mitosis and Cytokinesis
Background:
- M phase phosphoprotein 1 (MPP1) was initially identified as a G2/M transition-specific phosphoprotein.
- Its precise role in cellular processes, particularly mitosis, remained largely uncharacterized.
Purpose of the Study:
- To characterize the functional properties of human MPP1.
- To elucidate the role of MPP1 in cell division and cytokinesis.
Main Methods:
- Recombinant MPP1 protein expression and in vitro biochemical assays (microtubule binding, bundling, ATPase activity).
- Gliding assays using polarity-marked microtubules to determine motor directionality and speed.
- Cellular localization studies in cycling cells via microscopy.
- RNA interference (RNAi)-mediated suppression of MPP1 to assess its function in cell division.
Main Results:
- Recombinant MPP1 demonstrated microtubule-binding, microtubule-bundling, and microtubule-stimulated ATPase activities.
- MPP1 functions as a slow, plus-end-directed molecular motor, moving at 0.07 microm/s.
- Cellular localization revealed MPP1 in nuclei during interphase, diffuse in metaphase cytoplasm, and concentrated at the midbody during later mitosis.
- MPP1 suppression led to failed cell division late in cytokinesis.
Conclusions:
- MPP1 is identified as a novel kinesin-related protein and a plus-end-directed molecular motor.
- MPP1 plays a critical role in the completion of cytokinesis.
- MPP1 is a new mitotic molecular motor essential for successful cell division.