Nucleolin-Mediated RNA Localization Regulates Neuron Growth and Cycling Cell Size.

How can cells sense their own size to coordinate biosynthesis and metabolism with their growth needs? We recently proposed a motor-dependent bidirectional transport mechanism for axon length and cell size sensing, but the nature of the motor-transported size signals remained elusive. Here, we show that motor-dependent mRNA localization regulates neuronal growth and cycling cell size. We found that the RNA-binding protein nucleolin is associated with importin β1 mRNA in axons.

Surface apposition and multiple cell contacts promote myoblast fusion in Drosophila flight muscles.

Fusion of individual myoblasts to form multinucleated myofibers constitutes a widely conserved program for growth of the somatic musculature. We have used electron microscopy methods to study this key form of cell-cell fusion during development of the indirect flight muscles (IFMs) of Drosophila melanogaster. We find that IFM myoblast-myotube fusion proceeds in a stepwise fashion and is governed by apparent cross talk between transmembrane and cytoskeletal elements.

Lam6 Regulates the Extent of Contacts between Organelles.

Communication between organelles is crucial for eukaryotic cells to function as one coherent unit. An important means of communication is through membrane contact sites, where two organelles come into close proximity allowing the transport of lipids and small solutes between them. Contact sites are dynamic in size and can change in response to environmental or cellular stimuli; however, how this is regulated has been unclear.

A dynamic interface between vacuoles and mitochondria in yeast.

Cellular life depends on continuous transport of lipids and small molecules between mitochondria and the endomembrane system. Recently, endoplasmic reticulum-mitochondrial encounter structure (ERMES) was identified as an important yet nonessential contact for such transport. Using a high-content screen in yeast, we found a contact site, marked by Vam6/Vps39, between vacuoles (the yeast lysosomal compartment) and mitochondria, named vCLAMP (vacuole and mitochondria patch).

Neuronal accumulation of glucosylceramide in a mouse model of neuronopathic Gaucher disease leads to neurodegeneration.

Gaucher disease has recently received wide attention due to the unexpected discovery that it is a genetic risk factor for Parkinson's disease. Gaucher disease is caused by the defective activity of the lysosomal enzyme, glucocerebrosidase (GCase; GBA1), resulting in intracellular accumulation of the glycosphingolipids, glucosylceramide and psychosine. The rare neuronopathic forms of GD (nGD) are characterized by profound neurological impairment and neuronal cell death.

PfSec13 is an unusual chromatin-associated nucleoporin of Plasmodium falciparum that is essential for parasite proliferation in human erythrocytes.

In Plasmodium falciparum, the deadliest form of human malaria, the nuclear periphery has drawn much attention due to its role as a sub-nuclear compartment involved in virulence gene expression. Recent data have implicated components of the nuclear envelope in regulating gene expression in several eukaryotes. Special attention has been given to nucleoporins that compose the nuclear pore complex (NPC).

Deletion of cognate CD8 T cells by immature dendritic cells: a novel role for perforin, granzyme A, TREM-1, and TLR7.

Immature dendritic cells (imDCs) can have a tolerizing effect under normal conditions or after transplantation. However, because of the significant heterogeneity of this cell population, it is extremely difficult to study the mechanisms that mediate the tolerance induced or to harness the application of imDCs for clinical use. In the present study, we describe the generation of a highly defined population of imDCs from hematopoietic progenitors and the direct visualization of the fate of TCR-transgenic alloreactive CD4(+) and CD8(+) T cells after encountering cognate or noncognate imDCs.

A motor-driven mechanism for cell-length sensing.

Size homeostasis is fundamental in cell biology, but it is not clear how large cells such as neurons can assess their own size or length. We examined a role for molecular motors in intracellular length sensing.Computational simulations suggest that spatial information can be encoded by the frequency of an oscillating retrograde signal arising from a composite negative feedback loop between bidirectional motor-dependent signals.

Transendothelial migration of lymphocytes mediated by intraendothelial vesicle stores rather than by extracellular chemokine depots.

Chemokines presented by the endothelium are critical for integrin-dependent adhesion and transendothelial migration of naive and memory lymphocytes. Here we found that effector lymphocytes of the type 1 helper T cell (T(H)1 cell) and type 1 cytotoxic T cell (T(C)1 cell) subtypes expressed adhesive integrins that bypassed chemokine signals and established firm arrests on variably inflamed endothelial barriers. Nevertheless, the transendothelial migration of these lymphocytes strictly depended on signals from guanine nucleotide-binding proteins of the G(i) type and was promoted by multiple endothelium-derived inflammatory chemokines, even without outer endothelial surface exposure.

Mitochondria as a sequestration site for incomplete TCRβ peptides: the TCRβ transmembrane domain is a sufficient mitochondrial targeting signal.

The existence of incomplete T cell receptor (TCR) mRNA forms, including germline transcripts and products of unfruitful TCR rearrangements, has long been known. However, it is unclear whether these molecules are functional. We have previously shown that T cells also contain truncated TCRβ peptides that lack the N-terminal part and contain C-terminus sequences.

Distinct pathological patterns in relapsing-remitting and chronic models of experimental autoimmune enchephalomyelitis and the neuroprotective effect of glatiramer acetate.

The respective roles of inflammatory and neurodegenerative processes in the pathology of multiple sclerosis (MS) and in its animal model experimental autoimmune encephalomyelitis (EAE) are controversial. Novel treatment strategies aim to operate within the CNS to induce neuroprotection and repair processes in addition to their anti-inflammatory properties. In this study we analyzed and compared the in situ pathological manifestations of EAE utilizing two different models, namely the relapsing-remitting PLP-induced and the chronic MOG-induced diseases.

Kindlin-3 is required for the stabilization of TCR-stimulated LFA-1:ICAM-1 bonds critical for lymphocyte arrest and spreading on dendritic cells.

Kindlin-3 is a key lymphocyte function-associated antigen-1 (LFA-1) coactivator deleted in leukocyte adhesion deficiency-III (LAD-III). In the present study, we investigated the involvement of this adaptor in lymphocyte motility and TCR-triggered arrest on ICAM-1 or on dendritic cells (DCs). Kindlin-3-null primary T cells from a LAD-III patient migrated normally on the major lymph node chemokine CCL21 and engaged in normal TCR signaling.

3D nuclear architecture reveals coupled cell cycle dynamics of chromatin and nuclear pores in the malaria parasite Plasmodium falciparum.

The deadliest form of human malaria is caused by the protozoan parasite Plasmodium falciparum. The complex life cycle of this parasite is associated with tight transcriptional regulation of gene expression. Nuclear positioning and chromatin dynamics may play an important role in regulating P.

The Drosophila blood brain barrier is maintained by GPCR-dependent dynamic actin structures.

The blood brain barrier (BBB) is essential for insulation of the nervous system from the surrounding environment. In Drosophila melanogaster, the BBB is maintained by septate junctions formed between subperineurial glia (SPG) and requires the Moody/G protein-coupled receptor (GPCR) signaling pathway. In this study, we describe novel specialized actin-rich structures (ARSs) that dynamically form along the lateral borders of the SPG cells.

LC3 and GATE-16/GABARAP subfamilies are both essential yet act differently in autophagosome biogenesis.

Autophagy, a critical process for bulk degradation of proteins and organelles, requires conjugation of Atg8 proteins to phosphatidylethanolamine on the autophagic membrane. At least eight different Atg8 orthologs belonging to two subfamilies (LC3 and GATE-16/GABARAP) occur in mammalian cells, but their individual roles and modes of action are largely unknown. In this study, we dissect the activity of each subfamily and show that both are indispensable for the autophagic process in mammalian cells.

Axoplasm isolation from peripheral nerve.

Localized changes in the composition of axonal cytoplasm (axoplasm) are critical for many biological processes, including axon guidance, responses to injury, neurite outgrowth, and axon-glia interactions. Biochemical and molecular studies of these mechanisms have been heavily focused on in vitro systems because of the difficulty of obtaining subcellular extracts from mammalian tissues in vivo. As in vitro systems might not replicate the in vivo situation, reliable methods of axoplasm extraction from whole nerve would be helpful for mechanistic studies on axons.

Lymphocyte crawling and transendothelial migration require chemokine triggering of high-affinity LFA-1 integrin.

Endothelial chemokines are instrumental for integrin-mediated lymphocyte adhesion and transendothelial migration (TEM). By dissecting how chemokines trigger lymphocyte integrins to support shear-resistant motility on and across cytokine-stimulated endothelial barriers, we found a critical role for high-affinity (HA) LFA-1 integrin in lymphocyte crawling on activated endothelium. Endothelial-presented chemokines triggered HA-LFA-1 and adhesive filopodia at numerous submicron dots scattered underneath crawling lymphocytes.

Increased LIS1 expression affects human and mouse brain development.

Deletions of the PAFAH1B1 gene (encoding LIS1) in 17p13.3 result in isolated lissencephaly sequence, and extended deletions including the YWHAE gene (encoding 14-3-3epsilon) cause Miller-Dieker syndrome. We identified seven unrelated individuals with submicroscopic duplication in 17p13.

Incomplete T-cell receptor-beta peptides target the mitochondrion and induce apoptosis.

The default pathway of cell-surface T-cell receptor (TCR) complex formation, and the subsequent transport to the membrane, is thought to entail endoplasmic reticulum (ER) localization followed by proteasome degradation of the unassembled chains. We show herein an alternative pathway: short, incomplete peptide versions of TCRbeta naturally occur in the thymus. Such peptides, which have minimally lost the leader sequence or have been massively truncated, leaving only the very C terminus intact, are sorted preferentially to the mitochondrion.

Human oligodendrocytes derived from embryonic stem cells: Effect of noggin on phenotypic differentiation in vitro and on myelination in vivo.

In attempts to produce mature oligodendrocytes from human embryonic stem (huES) cells, we searched conditions inducing transcription factors Olig1/2, as well as Nkx2.2 and Sox10, which are needed for maturation. This was obtained by retinoic acid treatment followed by noggin, an antagonist of bone morphogenetic proteins (BMPs).

Shear flow-dependent integration of apical and subendothelial chemokines in T-cell transmigration: implications for locomotion and the multistep paradigm.

Lymphocyte extravasation requires that emigrating cells process chemoattractant signals, typically mediated by chemokines, encountered on endothelial surface (apical) and subendothelial (basal) compartments. These signals are delivered under conditions of hemodynamic shear, a fundamental feature of all physiologic leukocyte-endothelial interactions. To analyze lymphocyte responsiveness to spatially distributed chemokines and their effects on transendothelial migration (TEM) under hydrodynamic shear, we constructed a transwell-based flow assay.

Tyrosine phosphatases epsilon and alpha perform specific and overlapping functions in regulation of voltage-gated potassium channels in Schwann cells.

Tyrosine phosphatases (PTPs) epsilon and alpha are closely related and share several molecular functions, such as regulation of Src family kinases and voltage-gated potassium (Kv) channels. Functional interrelationships between PTPepsilon and PTPalpha and the mechanisms by which they regulate K+ channels and Src were analyzed in vivo in mice lacking either or both PTPs. Lack of either PTP increases Kv channel activity and phosphorylation in Schwann cells, indicating these PTPs inhibit Kv current amplitude in vivo.

Alpha4beta1-dependent adhesion strengthening under mechanical strain is regulated by paxillin association with the alpha4-cytoplasmic domain.

The capacity of integrins to mediate adhesiveness is modulated by their cytoplasmic associations. In this study, we describe a novel mechanism by which alpha4-integrin adhesiveness is regulated by the cytoskeletal adaptor paxillin. A mutation of the alpha4 tail that disrupts paxillin binding, alpha4(Y991A), reduced talin association to the alpha4beta1 heterodimer, impaired integrin anchorage to the cytoskeleton, and suppressed alpha4beta1-dependent capture and adhesion strengthening of Jurkat T cells to VCAM-1 under shear stress.

Chemokine receptor CXCR4-dependent internalization and resecretion of functional chemokine SDF-1 by bone marrow endothelial and stromal cells.

Regulation of the availability of chemokine SDF-1 (CXCL12) in bone marrow is still not fully understood. Here we describe a unique function for the chemokine receptor CXCR4 expressed on bone marrow endothelial cells, which efficiently internalize circulating SDF-1, resulting in its translocation into the bone marrow. Translocated SDF-1 increased the homing of transplanted human CD34(+) hematopoietic progenitors to the bone marrow.