The Dictyostelium type V myosin MyoJ is responsible for the cortical association and motility of contractile vacuole membranes

submitted by: JCB
The contractile vacuole (CV) complex in Dictyostelium is a tubulovesicular osmoregulatory organelle that exhibits extensive motility along the actin-rich cortex, providing a useful model for investigating myosin-dependent membrane transport. Here, we show that the type V myosin myoJ localizes to CV membranes and is required for efficient osmoregulation, the normal accumulation of CV membranes in the cortex, and the conversion of collapsed bladder membranes into outwardly radiating cortical...
Authors: G Jung, Ma Titus, Ja Hammer

Multiparametric analysis of focal adhesion formation by RNAi-mediated gene knockdown

submitted by: JCB
Cell adhesion to the extracellular matrix is mediated by elaborate networks of multiprotein complexes consisting of adhesion receptors, cytoskeletal components, signaling molecules, and diverse adaptor proteins. To explore how specific molecular pathways function in the assembly of focal adhesions (FAs), we performed a high-throughput, high-resolution, microscopy-based screen. We used small interfering RNAs (siRNAs) to target human kinases, phosphatases, and migration- and adhesion-related...
Authors: Sabina Winograd-katz, Shalev Itzkovitz, Zvi Kam, Benjamin Geiger

Motor-dependent microtubule disassembly driven by tubulin tyrosination

submitted by: JCB
In cells, stable microtubules (MTs) are covalently modified by a carboxypeptidase, which removes the C-terminal Tyr residue of alpha-tubulin. The significance of this selective detyrosination of MTs is not understood. In this study, we report that tubulin detyrosination in fibroblasts inhibits MT disassembly. This inhibition is relieved by overexpression of the depolymerizing motor mitotic centromere-associated kinesin (MCAK). Conversely, suppression of MCAK expression prevents disassembly...
Authors: Leticia Peris

Cdc42 controls spindle orientation to position the apical surface during epithelial morphogenesis

submitted by: JCB
The establishment of apical–basal polarity within a single cell and throughout a growing tissue is a key feature of epithelial morphogenesis. To examine the underlying mechanisms, the human intestinal epithelial cell line Caco-2 was grown in a three-dimensional matrix to generate a cystlike structure, where the apical surface of each epithelial cell faces a fluid-filled central lumen. A discrete apical domain is established as early as the first cell division and between the two daughter...
Authors: Aron Jaffe, Noriko Kaji, Joanne Durgan, Alan Hall

One-Dimensional Topography Underlies Three-Dimensional Fibrillar Cell Migration

submitted by: JCB
Current concepts of cell migration were established in regular two-dimensional (2D) cell culture, but the roles of topography are poorly understood for cells migrating in an oriented 3D fibrillar extracellular matrix (ECM). We use a novel micropatterning technique termed microphotopatterning (µPP) to identify functions for 1D fibrillar patterns in 3D cell migration. In striking contrast to 2D, cell migration in both 1D and 3D is rapid, uniaxial, independent of ECM ligand density, and...
Authors: Andrew Doyle, Francis Wang, Kazue Matsumoto

Collective cell migration requires vesicular trafficking for chemoattractant delivery at the trailing edge

submitted by: JCB
Chemoattractant signaling induces the polarization and directed movement of cells secondary to the activation of multiple effector pathways. In addition, chemotactic signals can be amplified and relayed to proximal cells via the synthesis and secretion of additional chemoattractant. The mechanisms underlying such remarkable features remain ill defined. We show that the asymmetrical distribution of adenylyl cyclase (ACA) at the back of Dictyostelium discoideum cells, an essential determinant...
Authors: Paul Kriebel, Valarie Barr, Erin Rericha, Guofeng Zhang, Carole Parent