Electric field–induced migration and intercellular stress alignment in a collective epithelial monolayer

Cho, Youngbin,Son, Minjeong,Jeong, Hyuntae,Shin, Jennifer H. American Society for Cell Biology 2018 Molecular biology of the cell Vol.29 No.19

<P>During wound healing, cells migrate with electrotactic bias as a collective entity. Unlike the case of the electric field (EF)-induced single-cell migration, the sensitivity of electrotactic response of the monolayer depends primarily on the integrity of the cell–cell junctions. Although there exist biochemical clues on how cells sense the EF, a well-defined physical portrait to illustrate how collective cells respond to directional EF remains elusive. Here, we developed an EF stimulating system integrated with a hydrogel-based traction measurement platform to quantify the EF-induced changes in cellular tractions, from which the complete in-plane intercellular stress tensor can be calculated. We chose immortalized human keratinocytes, HaCaT, as our model cells to investigate the role of EF in epithelial migration during wound healing. Immediately after the onset of EF (0.5 V/cm), the HaCaT monolayer migrated toward anode with ordered directedness and enhanced speed as early as 15 min. Cellular traction and intercellular stresses were gradually aligned perpendicular to the direction of the EF until 50 min. The EF-­induced reorientation of physical stresses was then followed by the delayed cell-body reorientation in the direction perpendicular to the EF. Once the intercellular stresses were aligned, the reversal of the EF direction redirected the reversed migration of the cells without any apparent disruption of the intercellular stresses. The results suggest that the dislodging of the physical stress alignment along the adjacent cells should not be necessary for changing the direction of the monolayer migration.</P>

Molecular Biology of the Cell: It's Our Journal.

American Society for Cell Biology 2005 Molecular biology of the cell Vol.16 No.1

Cdo Interacts with APPL1 and Activates AKT in Myoblast Differentiation

Bae, Gyu-Un,Lee, Jae-Rin,Kim, Bok-Geon,Han, Ji-Won,Leem, Young-Eun,Lee, Hey-Jin,Ho, Seok-Man,Hahn, Myong-Joon,Kang, Jong-Sun The American Society for Cell Biology 2010 Molecular biology of the cell Vol.21 No.14

<P>Cell–cell interactions between muscle precursors are required for myogenic differentiation; however, underlying mechanisms are largely unknown. Promyogenic cell surface protein Cdo functions as a component of multiprotein complexes containing other cell adhesion molecules, Boc, Neogenin and N-cadherin, and mediates some of signals triggered by cell–cell interactions between muscle precursors. Cdo activates p38MAPK via interaction with two scaffold proteins JLP and Bnip-2 to promote myogenesis. p38MAPK and Akt signaling are required for myogenic differentiation and activation of both signaling pathways is crucial for efficient myogenic differentiation. We report here that APPL1, an interacting partner of Akt, forms complexes with Cdo and Boc in differentiating myoblasts. Both Cdo and APPL1 are required for efficient Akt activation during myoblast differentiation. The defective differentiation of Cdo-depleted cells is fully rescued by overexpression of a constitutively active form of Akt, whereas overexpression of APPL1 fails to do so. Taken together, Cdo activates Akt through association with APPL1 during myoblast differentiation, and this complex likely mediates some of the promyogenic effect of cell–cell interaction. The promyogenic function of Cdo involves a coordinated activation of p38MAPK and Akt via association with scaffold proteins, JLP and Bnip-2 for p38MAPK and APPL1 for Akt.</P>

The Initial Enzyme for Glycosylphosphatidylinositol Biosynthesis Requires PIG-Y, a Seventh Component

Murakami, Yoshiko,Siripanyaphinyo, Uamporn,Hong, Yeongjin,Tashima, Yuko,Maeda, Yusuke,Kinoshita, Taroh American Society for Cell Biology 2005 Molecular biology of the cell Vol.16 No.11

<P>Biosynthesis of glycosylphosphatidylinositol (GPI) is initiated by an unusually complex GPI-N-acetylglucosaminyltransferase (GPI-GnT) consisting of at least six proteins. Here, we report that human GPI-GnT requires another component, termed PIG-Y, a 71 amino acid protein with two transmembrane domains. The Burkitt lymphoma cell line Daudi, severely defective in the surface expression of GPI-anchored proteins, was a null mutant of PIG-Y. A complex of six components was formed without PIG-Y. PIG-Y appeared to be directly associated with PIG-A, implying that PIG-Y is the key molecule that regulates GPI-GnT activity by binding directly to the catalytic subunit PIG-A. PIG-Y is probably homologous to yeast Eri1p, a component of GPI-GnT. We did not obtain evidence for a functional linkage between GPI-GnT and ras GTPases in mammalian cells as has been reported for yeast cells. A single transcript encoded PIG-Y and, to its 5′ side, another protein PreY that has homologues in a wide range of organisms and is characterized by a conserved domain termed DUF343. These two proteins are translated from one mRNA by leaky scanning of the PreY initiation site.</P>

Expansion of Chromosome Territories with Chromatin Decompaction in BAF53-depleted Interphase Cells.

Lee, Kiwon,Kang, Mi Jin,Kwon, Su Jin,Kwon, Yunhee Kim,Kim, Ki Woo,Lim, Jae-Hwan,Kwon, Hyockman American Society for Cell Biology 2007 Molecular biology of the cell Vol.18 No.10

<P>Chromosomes are compartmentalized into discrete chromosome territories during interphase in mammalian cells. A chromosome territory is generated by the tendency of chromatin to occupy the smallest shell volume, which is determined by the polymeric properties and interactions of the internal meshwork of the chromatin fiber. Here, we show that BAF53 knockdown by small interfering RNA interference led to the expansion of chromosome territories. This was accompanied by a reduction in chromatin compaction, an increase in the micrococcal nuclease sensitivity of the chromatin, and an alteration in H3-K9 and H3-K79 dimethylation. Interestingly, the BAF53 knockdown cells suffer a cell cycle defect. Despite the significant irregularity and decompaction of the polynucleosomes isolated from the BAF53 knockdown cells, the chromatin loading of H1 and core histones remained unaltered, as did the nucleosome spacing. The histone hyperacetylation and down-regulation of BRG-1, mBrm, and Tip49, the catalytic components of the SWI/SNF complex and the TIP60 complex, respectively, did not expand chromosome territories. These results indicate that BAF53 contributes to the polymeric properties and/or the internal meshwork interactions of the chromatin fiber probably via a novel mechanism.</P>

RKIKK Motif in the Intracellular Domain Is Critical for Spatial and Dynamic Organization of ICAM-1: Functional Implication for the Leukocyte Adhesion and Transmigration

Oh, Hyun-Mee,Lee, SungGa,Na, Bo-Ra,Wee, Hyun,Kim, Sang-Hyun,Choi, Suck-Chei,Lee, Kang-Min,Jun, Chang-Duk,Wang, Yu-li American Society for Cell Biology 2007 Molecular biology of the cell Vol.18 No.6

<P>No direct evidence has been reported whether the spatial organization of ICAM-1 on the cell surface is linked to its physiological function in terms of leukocyte adhesion and transendothelial migration (TEM). Here we observed that ICAM-1 by itself directly regulates the de novo elongation of microvilli and is thereby clustered on the microvilli. However, truncation of the intracellular domain resulted in uniform cell surface distribution of ICAM-1. Mutation analysis revealed that the C-terminal 21 amino acids are dispensable, whereas a segment of 5 amino acids (<SUP>507</SUP>RKIKK<SUP>511</SUP>) in the NH-terminal third of intracellular domain, is required for the proper localization and dynamic distribution of ICAM-1 and the association of ICAM-1 with F-actin, ezrin, and moesin. Importantly, deletion of the<SUP>507</SUP>RKIKK<SUP>511</SUP>significantly delayed the LFA-1-dependent membrane projection and decreased leukocyte adhesion and subsequent TEM. Endothelial cells treated with cell-permeant penetratin-ICAM-1 peptides comprising ICAM-1 RKIKK sequences inhibited leukocyte TEM. Collectively, these findings demonstrate that<SUP>507</SUP>RKIKK<SUP>511</SUP>is an essential motif for the microvillus ICAM-1 presentation and further suggest a novel regulatory role for ICAM-1 topography in leukocyte TEM.</P>

Nuclear hormone receptor corepressor promotes esophageal cancer cell invasion by transcriptional repression of interferon-γ–inducible protein 10 in a casein kinase 2–dependent manner

Yoo, Jung-Yoon,Choi, Hyo-Kyoung,Choi, Kyung-Chul,Park, Soo-Yeon,Ota, Ichiro,Yook, Jong In,Lee, Yoo-Hyun,Kim, Kunhong,Yoon, Ho-Geun The American Society for Cell Biology 2012 Molecular biology of the cell Vol.23 No.15

<P>Aberrant expression of casein kinase 2 (CK2) is associated with tumor progression; however, the molecular mechanism by which CK2 modulates tumorigenesis is incompletely understood. In this paper, we show that CK2α phosphorylates the C-terminal domain of the nuclear receptor corepressor (NCoR) at Ser-2436 to stabilize the NCoR against the ubiquitin-dependent proteasomal degradation pathway. Importantly, NCoR promoted the invasion of esophageal cancer cells in a CK2-dependent manner. By using cyclic DNA microarray analysis, we identified CXCL10/IP-10 as a novel CK2α-NCoR cascade–regulated gene. The depletion of both NCoR and HDAC3 commonly derepressed IP-10 transcription, demonstrating the functional engagement of the NCoR-HDAC3 axis in IP-10 transcriptional repression. Furthermore, chromatin immunoprecipitation assays showed that c-Jun recruits NCoR-HDAC3 corepressor complexes to the (AP1 site of IP-10, leading to histone hypoacetylation and IP-10 down-regulation. Collectively these data suggest that the CK2α-NCoR cascade selectively represses the transcription of IP-10 and promotes oncogenic signaling in human esophageal cancer cells.</P>

Nsk1 ensures accurate chromosome segregation by promoting association of kinetochores to spindle poles during anaphase B

Buttrick, Graham J.,Meadows, John C.,Lancaster, Theresa C.,Vanoosthuyse, Vincent,Shepperd, Lindsey A.,Hoe, Kwang-Lae,Kim, Dong-Uk,Park, Han-Oh,Hardwick, Kevin G.,Millar, Jonathan B. A. The American Society for Cell Biology 2011 Molecular biology of the cell Vol.22 No.23

<P>Type 1 phosphatase (PP1) antagonizes Aurora B kinase to stabilize kinetochore–microtubule attachments and to silence the spindle checkpoint. We screened for factors that exacerbate the growth defect of <I>Δdis2</I> cells, which lack one of two catalytic subunits of PP1 in fission yeast, and identified Nsk1, a novel protein required for accurate chromosome segregation. During interphase, Nsk1 resides in the nucleolus but spreads throughout the nucleoplasm as cells enter mitosis. Following dephosphorylation by Clp1 (Cdc14-like) phosphatase and at least one other phosphatase, Nsk1 localizes to the interface between kinetochores and the inner face of the spindle pole body during anaphase. In the absence of Nsk1, some kinetochores become detached from spindle poles during anaphase B. If this occurs late in anaphase B, then the sister chromatids of unclustered kinetochores segregate to the correct daughter cell. These unclustered kinetochores are efficiently captured, retrieved, bioriented, and segregated during the following mitosis, as long as Dis2 is present. However, if kinetochores are detached from a spindle pole early in anaphase B, then these sister chromatids become missegregated. These data suggest Nsk1 ensures accurate chromosome segregation by promoting the tethering of kinetochores to spindle poles during anaphase B.</P>

RPTPμ tyrosine phosphatase promotes adipogenic differentiation via modulation of p120 catenin phosphorylation

Kim, Won Kon,Jung, Hyeyun,Kim, Eun Young,Kim, Do Hyung,Cho, Yee Sook,Park, Byoung Chul,Park, Sung Goo,Ko, Yong,Bae, Kwang-Hee,Lee, Sang Chul The American Society for Cell Biology 2011 Molecular biology of the cell Vol.22 No.24

<P>Adipocyte differentiation can be regulated by the combined activity of protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs). In particular, PTPs act as key regulators in differentiation-associated signaling pathways. We recently found that receptor-type PTPμ (RPTPμ) expression is markedly increased during the adipogenic differentiation of 3T3-L1 preadipocytes and mesenchymal stem cells. Here, we investigate the functional roles of RPTPμ and the mechanism of its involvement in the regulation of signal transduction during adipogenesis of 3T3-L1 cells. Depletion of endogenous RPTPμ by RNA interference significantly inhibited adipogenic differentiation, whereas RPTPμ overexpression led to an increase in adipogenic differentiation. Ectopic expression of p120 catenin suppressed adipocyte differentiation, and the decrease in adipogenesis by p120 catenin was recovered by introducing RPTPμ. Moreover, RPTPμ induced a decrease in the cytoplasmic p120 catenin expression by reducing its tyrosine phosphorylation level, consequently leading to enhanced translocation of Glut-4 to the plasma membrane. On the basis of these results, we propose that RPTPμ acts as a positive regulator of adipogenesis by modulating the cytoplasmic p120 catenin level. Our data conclusively demonstrate that differentiation into adipocytes is controlled by RPTPμ, supporting the utility of RPTPμ and p120 catenin as novel target proteins for the treatment of obesity.</P>

The TAM-family receptor Mer mediates production of HGF through the RhoA-dependent pathway in response to apoptotic cells

Park, Hyun-Jung,Baen, Ji-Yeon,Lee, Ye-Ji,Choi, Youn-Hee,Kang, Jihee Lee The American Society for Cell Biology 2012 Molecular biology of the cell Vol.23 No.16

<P>The TAM receptor protein tyrosine kinases Tyro3, Axl, and Mer play important roles in macrophage function. We investigated the roles of the TAM receptors in mediating the induction of hepatocyte growth factor (HGF) during the interaction of macrophages with apoptotic cells. Mer-specific neutralizing antibody, small interfering RNA (siRNA), and a recombinant Mer protein (Mer/Fc) inhibited HGF mRNA and protein expression, as well as activation of RhoA, Akt, and specific mitogen-activated protein (MAP) kinases in response to apoptotic cells. Inhibition of Axl or Tyro3 with specific antibodies, siRNA, or Fc-fusion proteins did not prevent apoptotic cell–induced HGF mRNA and protein expression and did not inhibit activation of the postreceptor signaling molecules RhoA and certain MAP kinases, including extracellular signal-regulated protein kinase and c-Jun NH<SUB>2</SUB>-terminal kinase. However, Axl- and Tyro3-specific blockers did inhibit the activation of Akt and p38 MAP kinase in response to apoptotic cells. In addition, none of the TAM receptors mediated the effects of apoptotic cells on transforming growth factor-β or epidermal growth factor mRNA expression. However, they were involved in the induction of vascular endothelial growth factor mRNA expression. Our data provide evidence that when macrophages interact with apoptotic cells, only Mer of the TAM-family receptors is responsible for mediating transcriptional HGF production through a RhoA-dependent pathway.</P>