Biochim Biophys Acta. 2007 Jul 27; [Epub ahead of
print]Click here to read Links
Adherens and tight junctions: Structure, function and
connections to the actin cytoskeleton.
Hartsock A, Nelson WJ.
Departments of Molecular and Cellular Physiology,
Stanford University, Stanford, CA 94305-5430, USA.
Adherens junctions and Tight junctions comprise two
modes of cell-cell adhesion that provide different
functions. Both junctional complexes are proposed to
associate with the actin cytoskeleton, and formation and
maturation of cell-cell contacts involves reorganization
of the actin cytoskeleton. Adherens junctions initiate
cell-cell contacts, and mediate the maturation and
maintenance of the contact. Adherens junctions consist of
the transmembrane protein E-cadherin, and intracellular
components, p120-catenin, beta-catenin and alpha-catenin.
Tight junctions regulate the paracellular pathway for the
movement of ions and solutes in-between cells. Tight
junctions consist of the transmembrane proteins occludin
and claudin, and the cytoplasmic scaffolding proteins ZO1, -2, and -3. This review discusses the binding
interactions of the most studied proteins that occur
within each of these two junctional complexes and possible
modes of regulation of these interactions, and the
different mechanisms that connect and regulate
interactions with the actin cytoskeleton.
PMID: 17854762 [PubMed - as supplied by publisher]
Biol Cell. 2007 Aug;99(8):411-23.Click here to read Links
'Should I stay or should I go?': myosin V function in
organelle trafficking.
Desnos C, Huet S, Darchen F.
Institut de Biologie Physico-Chimique, Centre National
de la Recherche Scientifique, UPR 1929, Université Paris 7
Denis Diderot, Paris, France. claire.desnos@ibpc.fr
Actin- and microtubule-based motors can propel
different cargos along filaments. Within cells, they
control the distribution of membrane-bound compartments by
performing complementary tasks. Organelles make long
journeys along microtubules, with class V myosins ensuring
their capture and their dispersal in actin-rich regions.
Myosin Va is recruited on to diverse organelles, such as
melanosomes and secretory vesicles, by a mechanism
involving Rab GTPases. The role of myosin Va in the
recruitment of secretory vesicles at the plasma membrane
reveals that the cortical actin network cannot merely be
seen as a physical barrier hindering vesicle access to
release sites. In neurons, myosin Va controls the
targeting of IP(3) (inositol 1,4,5-trisphosphate)sensitive Ca(2+) stores to dendritic spines and the
transport of mRNAs. These defects probably account for the
severe neurological symptoms observed in Griscelli
syndrome due to mutations in the MYO5A gene.
PMID: 17635110 [PubMed - indexed for MEDLINE]
Annu Rev Biophys Biomol Struct. 2007;36:451-77.Click here
to read Links
Regulation of actin filament assembly by Arp2/3
complex and formins.
Pollard TD.
Department of Molecular, Cellular, and Developmental
Biology, Yale University, New Haven, Connecticut 065208103, USA. thomas.pollard@yale.edu
This review summarizes what is known about the
biochemical and biophysical mechanisms that initiate the
assembly of actin filaments in cells. Assembly and
disassembly of these filaments contribute to many types of
cellular movements. Numerous proteins regulate actin
assembly, but Arp2/3 complex and formins are the focus of
this review because more is known about them than other
proteins that stimulate the formation of new filaments.
Arp2/3 complex is active at the leading edge of motile
cells, where it produces branches on the sides of existing
filaments. Growth of these filaments produces force to
protrude the membrane. Crystal structures, reconstructions
from electron micrographs, and biophysical experiments
have started to map out the steps through which proteins
called nucleation-promoting factors stimulate the
formation of branches. Formins nucleate and support the
elongation of unbranched actin filaments for cytokinesis
and various types of actin filament bundles. Formins
associate processively with the fast-growing ends of
filaments and protect them from capping.
PMID: 17477841 [PubMed - indexed for MEDLINE]
Int Rev Cytol. 2007;258:1-82.Click here to read Links
Mechanism of depolymerization and severing of actin
filaments and its significance in cytoskeletal dynamics.
Ono S.
Department of Pathology, Emory University, Atlanta, GA
30322, USA.
The actin cytoskeleton is one of the major structural
components of the cell. It often undergoes rapid
reorganization and plays crucial roles in a number of
dynamic cellular processes, including cell migration,
cytokinesis, membrane trafficking, and morphogenesis.
Actin monomers are polymerized into filaments under
physiological conditions, but spontaneous depolymerization
is too slow to maintain the fast actin filament dynamics
observed in vivo. Gelsolin, actin-depolymerizing factor
(ADF)/cofilin, and several other actinsevering/depolymerizing proteins can enhance disassembly
of actin filaments and promote reorganization of the actin
cytoskeleton. This review presents advances as well as a
historical overview of studies on the biochemical
activities and cellular functions of actinsevering/depolymerizing proteins.
PMID: 17338919 [PubMed - indexed for MEDLINE]
Curr Opin Cell Biol. 2007 Feb;19(1):43-50. Epub 2006 Dec
20.Click here to read Links
Integrins and the actin cytoskeleton.
Delon I, Brown NH.
The Gurdon Institute and Dept of Physiology,
Development and Neuroscience, University of Cambridge,
Tennis Court Rd, Cambridge CB2 1QN.
The ability to connect to the actin cytoskeleton is a
key part of the adhesive function of integrins. This
linkage between integrins and the cytoskeleton involves a
large complex of integrin-associated proteins that
function in both the assembly and disassembly of the link.
Genetic evidence has helped to clarify the relative
contributions of different components of this link. In
different contexts integrins can either stimulate or
suppress actin based structures, indicating the variety of
pathways leading from integrins to the cytoskeleton. The
cytoskeleton also contributes to the extent of the
integrin junction, allowing an adhesive contact to attain
sufficient strength to resist contractile forces involved
in cellular movement and function.
PMID: 17184985 [PubMed - indexed for MEDLINE]
Curr Opin Cell Biol. 2007 Feb;19(1):51-6. Epub 2006 Dec
18.Click here to read Links
Understanding ERM proteins--the awesome power of
genetics finally brought to bear.
Hughes SC, Fehon RG.
Department of Cell Biology, University of Alberta,
Edmonton, Alberta, T6G 2H7, Canada.
In epithelial cells, the Ezrin, Radixin and Moesin
(ERM) proteins are involved in many cellular functions,
including regulation of actin cytoskeleton, control of
cell shape, adhesion and motility, and modulation of
signaling pathways. However, discerning the specific
cellular roles of ERMs has been complicated by redundancy
between these proteins. Recent genetic studies in model
organisms have identified unique roles for ERM proteins.
These include the regulation of morphogenesis and
maintenance of integrity of epithelial cells,
stabilization of intercellular junctions, and regulation
of the Rho small GTPase. These studies also suggest that
ERMs have roles in actomyosin contractility and vesicular
trafficking in the apical domain of epithelial cells.
Thus, genetic analysis has enhanced our understanding of
these widely expressed membrane-associated proteins.
PMID: 17175152 [PubMed - indexed for MEDLINE]
Curr Opin Cell Biol. 2007 Feb;19(1):51-6. Epub 2006 Dec
18.Click here to read Links
Understanding ERM proteins--the awesome power of
genetics finally brought to bear.
Hughes SC, Fehon RG.
Department of Cell Biology, University of Alberta,
Edmonton, Alberta, T6G 2H7, Canada.
In epithelial cells, the Ezrin, Radixin and Moesin
(ERM) proteins are involved in many cellular functions,
including regulation of actin cytoskeleton, control of
cell shape, adhesion and motility, and modulation of
signaling pathways. However, discerning the specific
cellular roles of ERMs has been complicated by redundancy
between these proteins. Recent genetic studies in model
organisms have identified unique roles for ERM proteins.
These include the regulation of morphogenesis and
maintenance of integrity of epithelial cells,
stabilization of intercellular junctions, and regulation
of the Rho small GTPase. These studies also suggest that
ERMs have roles in actomyosin contractility and vesicular
trafficking in the apical domain of epithelial cells.
Thus, genetic analysis has enhanced our understanding of
these widely expressed membrane-associated proteins.
PMID: 17175152 [PubMed - indexed for MEDLINE]
Oncogene. 2006 Dec 4;25(57):7538-44.Click here to read
Links
Wnt signalling and the actin cytoskeleton.
Akiyama T, Kawasaki Y.
Laboratory of Molecular and Genetic Information,
Institute for Molecular and Cellular Biosciences, The
University of Tokyo, Bunkyo-ku, Tokyo, Japan.
akiyama@imcbns.iam.u-tokyo.ac.jp
The tumour suppressor adenomatous polyposis coli (APC)
is mutated in sporadic and familial colorectal tumours.
APC binds to beta-catenin, a key component of the Wnt
signalling pathway, and induces its degradation. In
addition to this role, there is increasing evidence for
additional roles of APC, including the organization of
cytoskeletal networks. APC interacts with microtubules and
accumulates at their plus ends in membrane protrusions.
Also, it has been reported that APC is associated with the
plasma membrane in an actin-dependent manner. Moreover,
APC interacts with IQGAP1, an effector of Rac1 and Cdc42,
and APC-stimulated guanine nucleotide exchange factor
(Asef), a Rac1-specific guanine nucleotide exchange factor
(GEF). IQGAP1 mediates association of APC with cortical
actin in the leading edge of migrating cell and both
proteins are required for cell polarization and
directional migration. APC interacts with Asef and
stimulates its activity, thereby regulating the actin
cytoskeletal network, cell morphology, adhesion and
migration. Truncated mutant APCs present in colorectal
tumour cells activate Asef constitutively and contribute
to their aberrant migratory properties, which may be
important for adenoma formation as well as tumour
progression to invasive malignancy.
PMID: 17143298 [PubMed - indexed for MEDLINE]
Soldati T, Schliwa M.
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Abstract Powering membrane traffic in endocytosis and
recycling.
Nat Rev Mol Cell Biol. 2006 Dec;7(12):897-908. Epub 2006
Nov 8. Review.
PMID: 17139330 [PubMed - indexed for MEDLINE]
Smythe E, Ayscough KR.
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Actin regulation in endocytosis.
J Cell Sci. 2006 Nov 15;119(Pt 22):4589-98. Review.
PMID: 17093263 [PubMed - indexed for MEDLINE]
Goley ED, Welch MD.
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