title: F-actin asymmetry and the endoplasmic reticulum-associated TCC-1 protein contribute to stereotypic spindle movements in the Caenorhabditis elegans embryo.
abstract: The microtubule spindle apparatus dictates the plane of cell cleavage in animal cells. During development, dividing cells control the position of the spindle to determine the size, location, and fate of daughter cells. Spindle positioning depends on pulling forces that act between the cell periphery and astral microtubules. This involves dynein recruitment to the cell cortex by a heterotrimeric G-protein α subunit in complex with a TPR-GoLoco motif protein (GPR-1/2, Pins, LGN) and coiled-coil protein (LIN-5, Mud, NuMA). In this study, we searched for additional factors that contribute to spindle positioning in the one-cell Caenorhabditis elegans embryo. We show that cortical actin is not needed for Gα-GPR-LIN-5 localization and pulling force generation. Instead, actin accumulation in the anterior actually reduces pulling forces, possibly by increasing cortical rigidity. Examining membrane-associated proteins that copurified with GOA-1 Gα, we found that the transmembrane and coiled-coil domain protein 1 (TCC-1) contributes to proper spindle movements. TCC-1 localizes to the endoplasmic reticulum membrane and interacts with UNC-116 kinesin-1 heavy chain in yeast two-hybrid assays. RNA interference of tcc-1 and unc-116 causes similar defects in meiotic spindle positioning, supporting the concept of TCC-1 acting with kinesin-1 in vivo. These results emphasize the contribution of membrane-associated and cortical proteins other than Gα-GPR-LIN-5 in balancing the pulling forces that position the spindle during asymmetric cell division.
authors.affiliation: Developmental Biology, Bijvoet Center for Biomolecular Research.
authors.forename: Christian W H
authors.initials: CW
authors.lastname: Berends
authors.forename: Javier
authors.initials: J
authors.lastname: Muñoz
authors.forename: Vincent
authors.initials: V
authors.lastname: Portegijs
authors.forename: Ruben
authors.initials: R
authors.lastname: Schmidt
authors.forename: Ilya
authors.initials: I
authors.lastname: Grigoriev
authors.forename: Mike
authors.initials: M
authors.lastname: Boxem
authors.forename: Anna
authors.initials: A
authors.lastname: Akhmanova
authors.forename: Albert J R
authors.initials: AJ
authors.lastname: Heck
authors.forename: Sander
authors.initials: S
authors.lastname: van den Heuvel
mesh_terms: D000199:Actins / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D017173:Caenorhabditis elegans / Q000196:embryology / Q000235:genetics* / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D004625:Embryo, Nonmammalian; D004721:Endoplasmic Reticulum / Q000235:genetics* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000235:genetics / Q000378:metabolism; D016547:Kinesins / Q000235:genetics / Q000378:metabolism; D008540:Meiosis / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008870:Microtubules / Q000235:genetics / Q000378:metabolism; D034521:Nuclear Matrix-Associated Proteins / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D015398:Signal Transduction; D008941:Spindle Apparatus / Q000235:genetics* / Q000378:metabolism; D020798:Two-Hybrid System Techniques
chemical_list: D000199:Actins; D029742:Caenorhabditis elegans Proteins; D018797:Cell Cycle Proteins; C475458:G protein regulator 1, C elegans; C475459:G protein regulator 2, C elegans; D020730:Guanine Nucleotide Dissociation Inhibitors; D008565:Membrane Proteins; D034521:Nuclear Matrix-Associated Proteins; C586102:TCC-1 protein, C elegans; C404808:lin-5 protein, C elegans; D016547:Kinesins