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Cellular Logistics

Haruki Hasegawa, Mei Geng, Randal R Ketchem, Ling Liu, Kevin Graham, Frederick Jacobsen
Full-length immunoglobulins (Igs) are widely considered difficult to crystallize because of their large size, N-linked glycosylation, and flexible hinge region. However, numerous cases of intracellular Ig crystallization are reported in plasma cell dyscrasias. What makes some Ig clones more prone to crystallize during biosynthesis as well as the biochemical and cell biological requirements for this cryptic event are poorly understood. To investigate the underlying process of intracellular Ig crystallization we searched for model IgGs that can induce crystalline inclusions during recombinant overexpression...
2017: Cellular Logistics
Laura E Newman, Cara R Schiavon, Rachel E Turn, Richard A Kahn
Mitochondria are essential, dynamic organelles that regularly undergo both fusion and fission in response to cellular conditions, though mechanisms of the regulation of their dynamics are incompletely understood. We provide evidence that increased activity of the small GTPase ARL2 is strongly correlated with an increase in fusion, while loss of ARL2 activity results in a decreased rate of mitochondrial fusion. Strikingly, expression of activated ARL2 can partially restore the loss of fusion resulting from deletion of either mitofusin 1 (MFN1) or mitofusin 2 (MFN2), but not deletion of both...
2017: Cellular Logistics
Addison Rains, Yorisha Bryant, Kaitlyn A Dorsett, Austin Culver, Jamal Egbaria, Austin Williams, Matt Barnes, Raeann Lamere, Austin R Rossi, Stephanie C Waldrep, Caroline Wilder, Elliot Kliossis, Melanie L Styers
The yeast vacuole plays key roles in cellular stress responses. Here, we show that deletion of lvs1, the fission yeast homolog of the Chediak-Higashi Syndrome CHS1/LYST gene, increases vacuolar size, similar to deletion of the Rab4 homolog ypt4. Overexpression of lvs1-YFP rescued vacuolar size in ypt4Δ cells, but ypt4-YFP did not rescue lvs1Δ, suggesting that lvs1 may act downstream of ypt4. Vacuoles were capable of hypotonic shock-induced fusion and recovery in both ypt4Δ and lvs1Δ cells, although recovery may be slightly delayed in ypt4Δ...
2017: Cellular Logistics
Amber Ismael, David E Stone
The ability of cells to direct their movement and growth in response to shallow chemical gradients is essential in the life cycles of all eukaryotic organisms. The signaling mechanisms underlying directional sensing in chemotactic cells have been well studied; however, relatively little is known about how chemotropic cells interpret chemical gradients. Recent studies of chemotropism in budding and fission yeast have revealed 2 quite different mechanisms-biased wandering of the polarity complex, and differential internalization of the receptor and G protein...
2017: Cellular Logistics
Theodore Busby, Justyna M Meissner, Melanie L Styers, Jay Bhatt, Akhil Kaushik, Anita B Hjelmeland, Elizabeth Sztul
No abstract text is available yet for this article.
2017: Cellular Logistics
Thomas E Hall, Nick Martel, Harriet P Lo, Zherui Xiong, Robert G Parton
The zebrafish is an emerging model for highly sophisticated medium-throughput experiments such as genetic and chemical screens. However, studies of entire protein families within this context are often hampered by poor genetic resources such as clone libraries. Here we describe a complete collection of 76 full-length open reading frame clones for the zebrafish rab protein family. While the mouse genome contains 60 rab genes and the human genome 63, we find that 18 zebrafish rab genes have 2, and in the case of rab38, 3 paralogues...
2017: Cellular Logistics
Rebecca McRae, Lynne A Lapierre, Elizabeth H Manning, James R Goldenring
MARK2/Par1b/EMK1, a serine/threonine kinase, is required for correct apical/basolateral membrane polarization in epithelial cells. However, the specific substrates mediating MARK2 action are less well understood. We have now found that MARK2 phosphorylates Rab11-FIP1B/C at serine 234 in a consensus site similar to that previously identified in Rab11-FIP2. In MDCK cells undergoing repolarization after a calcium switch, antibodies specific for pS234-Rab11-FIP1 or pS227-Rab11-FIP2 demonstrate that the spatial and temporal activation of Rab11-FIP1 phosphorylation is distinct from that for Rab11-FIP2...
2017: Cellular Logistics
Yuantai Wu, Mehmet Takar, Andrea A Cuentas-Condori, Todd R Graham
NEO1 is an essential gene in budding yeast and belongs to a highly conserved subfamily of P-type ATPase genes that encode phospholipid flippases. Inactivation of temperature sensitive neo1(ts) alleles produces pleiomorphic defects in the secretory and endocytic pathways, including fragmented vacuoles. A screen for multicopy suppressors of neo1-2(ts) growth defects yielded YPT7, which encodes a Rab7 homolog involved in SNARE-dependent vacuolar fusion. YPT7 suppressed the vacuole fragmentation phenotype of neo1-2, but did not suppress Golgi-associated protein trafficking defects...
July 2016: Cellular Logistics
Juan J Barrero, Effrosyni Papanikou, Jason C Casler, Kasey J Day, Benjamin S Glick
FK506-binding protein (FKBP) is a monomer that binds to FK506, rapamycin, and related ligands. The F36M substitution, in which Phe36 in the ligand-binding pocket is changed to Met, leads to formation of antiparallel FKBP dimers, which can be dissociated into monomers by ligand binding. This FKBP(M) mutant has been employed in the mammalian secretory pathway to generate aggregates that can be dissolved by ligand addition to create cargo waves. However, when testing this approach in yeast, we found that dissolution of FKBP(M) aggregates was inefficient...
July 2016: Cellular Logistics
Neeladri Sekhar Roy, Marielle E Yohe, Paul A Randazzo, James M Gruschus
Pleckstrin Homology (PH) domains bind phospholipids and proteins. They are critical regulatory elements of a number enzymes including guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs) for Ras-superfamily guanine nucleotide binding proteins such as ADP-ribosylation factors (Arfs). Recent studies have indicated that many PH domains may bind more than one ligand cooperatively. Here we discuss the molecular basis of PH domain-dependent allosteric behavior of 2 ADP-ribosylation factor exchange factors, Grp1 and Brag2, cooperative binding of ligands to the PH domains of Grp1 and the Arf GTPase-activating protein, ASAP1, and the consequences for activity of the associated catalytic domains...
April 2016: Cellular Logistics
Laura E Newman, Cara Schiavon, Richard A Kahn
We describe the construction and uses of a series of plasmids for directing expression to varied levels of exogenous proteins targeted to the mitochondrial matrix or intermembrane space. We found that the level of protein expression achieved, the kinetics of expression and mitochondrial import, and half-life after import can each vary with the protein examined. These factors should be considered when directing localization of an exogenous protein to mitochondria for rescue, proteomics, or other approaches. We describe the construction of a collection of plasmids for varied expression of proteins targeted to the mitochondrial matrix or intermembrane space, using previously defined targeting sequences and strength CMV promoters...
2016: Cellular Logistics
Jennifer L Stow
No abstract text is available yet for this article.
January 2016: Cellular Logistics
Christopher M Hickey
Elaborate control of gene expression by transcription factors is common to all kingdoms of life. In eukaryotes, transcription factor abundance and activity are often regulated by targeted proteolysis via the ubiquitin-proteasome system (UPS). The yeast MATα2 (α2) cell type regulator has long served as a model for UPS-dependent transcription factor degradation. Proteolysis of α2 is complex: it involves at least 2 ubiquitylation pathways and multiple regions of α2 affect its degradation. Such complexity also exists for the degradation of other UPS substrates...
January 2016: Cellular Logistics
Jeremy C Yeo, Adam A Wall, Lin Luo, Jennifer L Stow
The phagocytosis and destruction of pathogens and dead cells by macrophages is important for innate immunity and tissue maintenance. Multiple Rab family GTPases engage effector molecules to coordinate the early stages of phagocytosis, which include rapid changes in actin polymerization, membrane phospholipids, trafficking and the activation of receptors. Defining the spatiotemporal, sequential recruitment of these Rabs is critical for insights into how phagocytosis is initiated and coordinated. Here, we screened GFP-tagged Rabs expressed in fixed and live cells to identify and stratify those recruited to early phagocytic membranes at stages defined by phospholipid transitions...
January 2016: Cellular Logistics
Tanmay Sanjeev Chavan, Serena Muratcioglu, Richard Marszalek, Hyunbum Jang, Ozlem Keskin, Attila Gursoy, Ruth Nussinov, Vadim Gaponenko
Ras GTPases activate more than 20 signaling pathways, regulating such essential cellular functions as proliferation, survival, and migration. How Ras proteins control their signaling diversity is still a mystery. Several pieces of evidence suggest that the plasma membrane plays a critical role. Among these are: (1) selective recruitment of Ras and its effectors to particular localities allowing access to Ras regulators and effectors; (2) specific membrane-induced conformational changes promoting Ras functional diversity; and (3) oligomerization of membrane-anchored Ras to recruit and activate Raf...
October 2015: Cellular Logistics
Sharon A Swanger, Alexa L Mattheyses, Erik G Gentry, Jeremy H Herskowitz
Communication among neurons is mediated through synaptic connections between axons and dendrites, and most excitatory synapses occur on actin-rich protrusions along dendrites called dendritic spines. Dendritic spines are structurally dynamic, and synapse strength is closely correlated with spine morphology. Abnormalities in the size, shape, and number of dendritic spines are prevalent in neurologic diseases, including autism spectrum disorders, schizophrenia, and Alzheimer disease. However, therapeutic targets that influence spine morphology are lacking...
October 2015: Cellular Logistics
Shana C Kerr, Richard A Kahn
No abstract text is available yet for this article.
July 2015: Cellular Logistics
Divya Khatter, Aastha Sindhwani, Mahak Sharma
Lysosomes are dynamic organelles that not only mediate degradation of cellular substrates but also play critical roles in processes such as cholesterol homeostasis, plasma membrane repair, antigen presentation, and cell migration. The small GTPase Arl8, a member of Arf-like (Arl) family of proteins, has recently emerged as a crucial regulator of lysosome positioning and membrane trafficking toward lysosomes. Through interaction with its effector SKIP, the human Arl8 paralog (Arl8b) mediates kinesin-1 dependent motility of lysosomes on microtubule tracks toward the cell periphery...
July 2015: Cellular Logistics
Shuwei Xie, Naava Naslavsky, Steve Caplan
Diacylglycerol kinases (DGKs) belong to a family of cytosolic kinases that regulate the phosphorylation of diacylglycerol (DAG), converting it into phosphatidic acid (PA). There are 10 known mammalian DGK isoforms, each with a different tissue distribution and substrate specificity. These differences allow regulation of cellular responses by fine-tuning the delicate balance of cellular DAG and PA. DGK isoforms are best characterized as mediators of signal transduction and immune function. However, since recent studies reveal that DAG and PA are also involved in the regulation of endocytic trafficking, it is therefore anticipated that DGKs also plays an important role in membrane trafficking...
April 2015: Cellular Logistics
Heike Fölsch
Epithelial cells are important for organ development and function. To this end, they polarize their plasma membrane into biochemically and physically distinct membrane domains. The apical membrane faces the luminal site of an organ and the basolateral domain is in contact with the basement membrane and neighboring cells. To establish and maintain this polarity it is important that newly synthesized and endocytic cargos are correctly sorted according to their final destinations at either membrane. Sorting takes place at one of 2 major sorting stations in the cells, the trans-Golgi network (TGN) and recycling endosomes (REs)...
April 2015: Cellular Logistics
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