scholarly journals Vesicle Navigation of Microtubule Ends Distinguished by A Single Rate-Constant Model

2020 ◽  
Author(s):  
M.W. Gramlich ◽  
S. Balseiro Gómez ◽  
S. M. Ali Tabei ◽  
M. Parkes ◽  
S. Yogev
Keyword(s):  
Rate Constant ◽  
Reverse Direction ◽  
Microtubule Cytoskeleton ◽  
Retrograde Motion ◽  
C Elegans ◽  
Transport Vesicles ◽  
Presynaptic Vesicle ◽  
Time Required

AbstractAxonal motor driven cargo utilizes the microtubule cytoskeleton in order to direct cargo, such as presynaptic vesicle precursors, to where they are needed. This transport requires vesicles to travel up to microns in distance. It has recently been observed that finite microtubule lengths can act as roadblocks inhibiting vesicles and increasing the time required for transport. Vesicles reach the end of a microtubule and pause until they can navigate to a neighboring microtubule in order to continue transport. The mechanism by which axonal vesicles navigate the end of a microtubule in order to continue mobility is unknown. In this manuscript we model experimentally observed vesicle pausing at microtubule ends in C. elegans. We show that a single rate-constant model reproduces the time vesicles pause at MT-ends. This model is based on the time a vesicle must detach from its current microtubule and re-attach to a neighboring microtubule. We show that vesicle pause times are different for anterograde and retrograde motion, suggesting that vesicles utilize different proteins at plus and minus end sites. Last, we show that vesicles do not likely utilize a tug-of-war like mechanism and reverse direction in order to navigate microtubule ends.

scholarly journals Distinguishing synaptic vesicle precursor navigation of microtubule ends with a single rate constant model

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
M. W. Gramlich ◽  
S. Balseiro-Gómez ◽  
S. M. Ali Tabei ◽  
M. Parkes ◽  
S. Yogev
Keyword(s):  
Synaptic Vesicle ◽  
Rate Constant ◽  
Reverse Direction ◽  
Microtubule Cytoskeleton ◽  
Retrograde Motion ◽  
C Elegans ◽  
Time Required

AbstractAxonal motor driven cargo utilizes the microtubule cytoskeleton in order to direct cargo, such as synaptic vesicle precursors (SVP), to where they are needed. This transport requires vesicles to travel up to microns in distance. It has recently been observed that finite microtubule lengths can act as roadblocks inhibiting SVP and increasing the time required for transport. SVPs reach the end of a microtubule and pause until they can navigate to a neighboring microtubule in order to continue transport. The mechanism(s) by which axonal SVPs navigate the end of a microtubule in order to continue mobility is unknown. In this manuscript we model experimentally observed vesicle pausing at microtubule ends in C. elegans. We show that a single rate-constant model reproduces the time SVPs pause at MT-ends. This model is based on the time an SVP must detach from its current microtubule and re-attach to a neighboring microtubule. We show that vesicle pause times are different for anterograde and retrograde motion, suggesting that vesicles utilize different proteins at plus and minus end sites. Last, we show that vesicles do not likely utilize a tug-of-war like mechanism and reverse direction in order to navigate microtubule ends.

scholarly journals DAPK interacts with Patronin and the microtubule cytoskeleton in epidermal development and wound repair

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Marian Chuang ◽  
Tiffany I Hsiao ◽  
Amy Tong ◽  
Suhong Xu ◽  
Andrew D Chisholm
Keyword(s):  
Innate Immunity ◽  
Wound Repair ◽  
Loss Of Function ◽  
Physical Damage ◽  
Microtubule Cytoskeleton ◽  
C Elegans ◽  
Tissue Integrity ◽  
Pharmacological Tests ◽  
Death Associated Protein Kinase ◽  
Dependent Transport

Epidermal barrier epithelia form a first line of defense against the environment, protecting animals against infection and repairing physical damage. In C. elegans, death-associated protein kinase (DAPK-1) regulates epidermal morphogenesis, innate immunity and wound repair. Combining genetic suppressor screens and pharmacological tests, we find that DAPK-1 maintains epidermal tissue integrity through regulation of the microtubule (MT) cytoskeleton. dapk-1 epidermal phenotypes are suppressed by treatment with microtubule-destabilizing drugs and mimicked or enhanced by microtubule-stabilizing drugs. Loss of function in ptrn-1, the C. elegans member of the Patronin/Nezha/CAMSAP family of MT minus-end binding proteins, suppresses dapk-1 epidermal and innate immunity phenotypes. Over-expression of the MT-binding CKK domain of PTRN-1 triggers epidermal and immunity defects resembling those of dapk-1 mutants, and PTRN-1 localization is regulated by DAPK-1. DAPK-1 and PTRN-1 physically interact in co-immunoprecipitation experiments, and DAPK-1 itself undergoes MT-dependent transport. Our results uncover an unexpected interdependence of DAPK-1 and the microtubule cytoskeleton in maintenance of epidermal integrity.

scholarly journals Interactions of plant acetohydroxy acid isomeroreductase with reaction intermediate analogues: correlation of the slow, competitive, inhibition kinetics of enzyme activity and herbicidal effects

1994 ◽  
Vol 301 (3) ◽  
pp. 813-820 ◽  
Author(s):  
R Dumas ◽  
C Cornillon-Bertrand ◽  
P Guigue-Talet ◽  
P Genix ◽  
R Douce ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Rate Constant ◽  
Spinacia Oleracea ◽  
Competitive Inhibition ◽  
Irreversible Inhibitor ◽  
Reaction Intermediate ◽  
Herbicide Activity ◽  
Time Required

N-Hydroxy-N-isopropyloxamate (IpOHA) is known to inhibit extremely tightly (Ki of 22 pM) the bacterial acetohydroxy acid isomeroreductase (EC 1.1.1.86) [Aulabaugh and Schloss (1990) Biochemistry 29, 2824-2830], the second enzyme of the branched-chain-amino-acid-biosynthetic pathway. Yet, although the same pathway exists in plant cells, this compound presents only very poor herbicidal action. Towards the goal of gaining a better understanding of this behaviour, we have studied the mechanism of interaction of this compound with a highly purified acetohydroxy acid isomeroreductase of plant origin, i.e. the spinach (Spinacia oleracea) chloroplast enzyme. IpOHA behaved as a nearly irreversible inhibitor of the enzyme. Encounter complex formation was very slow (association rate constant 1.9 x 10(3) M-1.s-1) and involved a single bimolecular step. Since inhibition was competitive with respect to acetohydroxy acid substrates, the time needed to achieve substantial (90%) inhibition in vitro of enzyme activity in the simultaneous presence of substrates and inhibitors was extremely long (for example of the order of hours at 1 microM IpOHA and 100 microM acetohydroxy acid substrates). Thus, under in vivo conditions, binding of the inhibitor may be so slow that it may delay considerably the time required for inhibition of the target enzyme. Simialr kinetic behaviour was observed with another reaction intermediate analogue described by Schulz, Spönemann, Köcher and Wengenmayer [(1988) FEBS Lett. 238, 375-378], 2-dimethyl-phosphinoyl-2-hydroxyacetic acid (Hoe 704), which displays a higher herbicide activity than IpOHA. The herbicidal potency of these two compounds appeared to be correlated with their rates of association with the plant acetohydroxy acid isomeroreductase, since the bimolecular rate constant for Hoe 704 (2.2 x 10(4) M-1.s-1) was higher than that for IpOHA.

scholarly journals Adaptins

2001 ◽  
Vol 12 (10) ◽  
pp. 2907-2920 ◽  
Author(s):  
Markus Boehm ◽  
Juan S. Bonifacino
Keyword(s):  
Arabidopsis Thaliana ◽  
Intracellular Transport ◽  
Adaptor Protein ◽  
Fruit Fly ◽  
C Elegans ◽  
Transport Vesicles ◽  
Intron Structure ◽  
Related Proteins ◽  
Selection Of ◽  
Plant Arabidopsis Thaliana

Adaptins are subunits of adaptor protein (AP) complexes involved in the formation of intracellular transport vesicles and in the selection of cargo for incorporation into the vesicles. In this article, we report the results of a survey for adaptins from sequenced genomes including those of man, mouse, the fruit fly Drosophila melanogaster, the nematode Caenorhabditis elegans, the plant Arabidopsis thaliana, and the yeasts, Saccharomyces cerevisiae andSchizosaccharomyces pombe. We find that humans, mice, and Arabidopsis thaliana have four AP complexes (AP-1, AP-2, AP-3, and AP-4), whereas D. melanogaster,C. elegans, S. cerevisiae, and S. pombe have only three (AP-1, AP-2, and AP-3). Additional diversification of AP complexes arises from the existence of adaptin isoforms encoded by distinct genes or resulting from alternative splicing of mRNAs. We complete the assignment of adaptins to AP complexes and provide information on the chromosomal localization, exon-intron structure, and pseudogenes for the different adaptins. In addition, we discuss the structural and evolutionary relationships of the adaptins and the genetic analyses of their function. Finally, we extend our survey to adaptin-related proteins such as the GGAs and stonins, which contain domains homologous to the adaptins.

Coagulation of homogenized milk particles by rennet

1984 ◽  
Vol 51 (3) ◽  
pp. 417-424 ◽  
Author(s):  
Elizabeth W. Robson ◽  
Douglas G. Dalgleish
Keyword(s):  
Light Scattering ◽  
Ionic Strength ◽  
Rate Constant ◽  
Skim Milk ◽  
Mutual Interaction ◽  
Time Required ◽  
Increasing Temperature

SummaryThe action of rennet on homogenized milk was studied using turbidimetric and light scattering techniques, and compared with results obtained previously for skim milk. The time required for the onset of coagulation was shorter for homogenized milk than for skim milk. The rate of coagulation of fully renneted particles increased with increasing temperature, and with increasing Ca2+ concentration, but was only slightly influenced by changes in ionic strength. The von Smoluchowski rate constant for the coagulation reaction was two orders of magnitude smaller for homogenized milk than for skim milk. Results suggest that coagulation of homogenized milk is controlled in general by the same factors as skim milk, and that the reaction may be inhibited owing to a reduction in the amount of casein available for mutual interaction, rather than to disruption of the micelles on homogenization.

Attraction of a Free-Living Nematode, Caenorhabditis elegans, to Foodborne Pathogenic Bacteria and Its Potential as a Vector of Salmonella Poona for Preharvest Contamination of Cantaloupe

2003 ◽  
Vol 66 (11) ◽  
pp. 1964-1971 ◽  
Author(s):  
KRISHAUN N. CALDWELL ◽  
GARY L. ANDERSON ◽  
PHILLIP L. WILLIAMS ◽  
LARRY R. BEUCHAT
Keyword(s):  
Caenorhabditis Elegans ◽  
Foodborne Pathogens ◽  
Pathogenic Bacteria ◽  
Fruits And Vegetables ◽  
Test Model ◽  
Human Pathogens ◽  
Free Living ◽  
Bacterial Colony ◽  
C Elegans ◽  
Time Required

Caenorhabditis elegans was studied to determine the potential role of free-living microbivorous nematodes as vectors for preharvest contamination of fruits and vegetables with foodborne pathogens. The propensity of C. elegans to be attracted to seven strains of Escherichia coli O157:H7, eight serotypes of Salmonella, six strains of Listeria monocytogenes, and cantaloupe juice was investigated. Twenty to 30 adult worms were placed on the surface of K agar midway between a 24-h bacterial colony and 10 μl of uninoculated tryptic soy broth (TSB) or cantaloupe juice positioned 1.5 cm apart. The numbers of nematodes that migrated to the colony, to the TSB, and to the cantaloupe juice within 5, 10, 15, and 20 min at 21°C were determined, and then the plates were incubated at 37°C for up to 7 days to determine the ability of C. elegans to survive and reproduce in bacterial colonies. The nematode was attracted to colonies of all test pathogens and survived and reproduced within colonies for up to 7 days. C. elegans was not attracted to cantaloupe juice. The potential of C. elegans to serve as a vector for the transport of Salmonella Poona to cantaloupe rinds was investigated. Adult worms that had been immersed in a suspension of Salmonella Poona were deposited 1 or 3 cm below the surface of soil on which a piece of cantaloupe rind was placed. The rind was analyzed for the presence of Salmonella Poona after 1, 3, 7, and 10 days at 21°C. The presence of Salmonella Poona was evident more quickly on rinds positioned on soil beneath which C. elegans inoculated with Salmonella Poona was initially deposited than on rinds positioned on soil beneath which Salmonella Poona alone was deposited. The time required to detect Salmonella Poona on rinds was longer when the rind was placed 3 cm above the inoculum than when the rind was placed 1 cm above the inoculum. Free-living nematodes may play a role in the preharvest dispersal of incidental human pathogens in soil to the surfaces of raw fruits and vegetables in contact with soil during development and maturation, as evidenced by the behavior of C. elegans as a test model.

scholarly journals SURO-2/TMEM39 Facilitates Collagen Secretion through the Formation of Large COPII Vesicles

2020 ◽  
Author(s):  
Kiho Lee ◽  
Jee Young Sung ◽  
Saerom Lee ◽  
Gaeun Lim ◽  
Kyung Jin Jung ◽  
...  
Keyword(s):  
Critical Factor ◽  
C Elegans ◽  
Golgi Transport ◽  
Collagen Secretion ◽  
Transport Vesicles ◽  
Transmission Electron ◽  
Copii Vesicle ◽  
Copii Vesicles ◽  
General Transport ◽  
Cuticle Thickness

Abstract Fibrosis of various tissues is a typical disease caused by excessive production and secretion of extracellular matrix. We used Caenorhabditis elegans to investigate the formation of large transport vesicles to understand collagen secretion, a critical factor in fibrosis formation. The suro-2 mutant displays obvious defects in collagen secretion and cuticle structure including a rupture phenotype in early adults. Transmission electron microscopy exhibited that the cuticle thickness of the suro-2 mutant was severely reduced. SURO-2/TMEM39 has 8 transmembrane domains and localizes in the endoplasmic reticulum (ER) membrane. SURO-2 interacts directly with NPP-20/Sec13, a component of the coat protein II (COPII) complex responsible for ER-to-Golgi transport. SURO-2 and NPP-20 localized at the same large puncta, a large COPII vesicle enough to accommodate collagens. We report here that SURO-2/TMEM39 is highly conserved among animal species and is a specialized regulator of bulky collagen secretion rather than general transport in C. elegans.

Distribution of tubulin, kinesin, and dynein in light- and dark-adapted octopus retinas

2000 ◽  
Vol 17 (1) ◽  
pp. 127-138 ◽  
Author(s):  
JUANA M. MARTINEZ ◽  
HASSAN ELFARISSI ◽  
BEGONA De VELASCO ◽  
GINA H. OCHOA ◽  
ARIA M. MILLER ◽  
...  
Keyword(s):  
Confocal Microscopy ◽  
Motor Proteins ◽  
Pigment Granule ◽  
Cytoskeletal Proteins ◽  
Actin Binding ◽  
Microtubule Cytoskeleton ◽  
Transport Pathways ◽  
Transport Vesicles ◽  
Pigment Granule Migration ◽  
Cytoskeletal Rearrangements

Cephalopod retinas exhibit several responses to light and dark adaptation, including rhabdom size changes, photopigment movements, and pigment granule migration. Light- and dark-directed rearrangements of microfilament and microtubule cytoskeletal transport pathways could drive these changes. Recently, we localized actin-binding proteins in light-/dark-adapted octopus rhabdoms and suggested that actin cytoskeletal rearrangements bring about the formation and degradation of rhabdomere microvilli subsets. To determine if the microtubule cytoskeleton and associated motor proteins control the other light/dark changes, we used immunoblotting and immunocytochemical procedures to map the distribution of tubulin, kinesin, and dynein in dorsal and ventral halves of light- and dark-adapted octopus retinas. Immunoblots detected α- and β-tubulin, dynein intermediate chain, and kinesin heavy chain in extracts of whole retinas. Epifluorescence and confocal microscopy showed that the tubulin proteins were distributed throughout the retina with more immunoreactivity in retinas exposed to light. Kinesin localization was heavy in the pigment layer of light- and dark-adapted ventral retinas but was less prominent in the dorsal region. Dynein distribution also varied in dorsal and ventral retinas with more immunoreactivity in light- and dark-adapted ventral retinas and confocal microscopy emphasized the granular nature of this labeling. We suggest that light may regulate the distribution of microtubule cytoskeletal proteins in the octopus retina and that position, dorsal versus ventral, also influences the distribution of motor proteins. The microtubule cytoskeleton is most likely involved in pigment granule migration in the light and dark and with the movement of transport vesicles from the photoreceptor inner segments to the rhabdoms.

scholarly journals The Caenorhabditis elegans GARP complex contains the conserved Vps51 subunit and is required to maintain lysosomal morphology

2011 ◽  
Vol 22 (14) ◽  
pp. 2564-2578 ◽  
Author(s):  
L. Luo ◽  
M. Hannemann ◽  
S. Koenig ◽  
J. Hegermann ◽  
M. Ailion ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Functional Characterization ◽  
Snare Complex ◽  
Synthetic Lethal ◽  
C Elegans ◽  
Yeast Two Hybrid System ◽  
Transport Vesicles ◽  
Two Hybrid ◽  
Garp Complex

In yeast the Golgi-associated retrograde protein (GARP) complex is required for tethering of endosome-derived transport vesicles to the late Golgi. It consists of four subunits—Vps51p, Vps52p, Vps53p, and Vps54p—and shares similarities with other multimeric tethering complexes, such as the conserved oligomeric Golgi (COG) and the exocyst complex. Here we report the functional characterization of the GARP complex in the nematode Caenorhabditis elegans. Furthermore, we identified the C. elegans Vps51 subunit, which is conserved in all eukaryotes. GARP mutants are viable but show lysosomal defects. We show that GARP subunits bind specific sets of Golgi SNAREs within the yeast two-hybrid system. This suggests that the C. elegans GARP complex also facilitates tethering as well as SNARE complex assembly at the Golgi. The GARP and COG tethering complexes may have overlapping functions for retrograde endosome-to-Golgi retrieval, since loss of both complexes leads to a synthetic lethal phenotype.

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