scholarly journals Structure of spastin bound to a glutamate-rich peptide implies a hand-over-hand mechanism of substrate translocation

2019 ◽  
Vol 295 (2) ◽  
pp. 435-443 ◽  
Author(s):  
Han Han ◽  
Heidi L. Schubert ◽  
John McCullough ◽  
Nicole Monroe ◽  
Michael D. Purdy ◽  
...  
Keyword(s):  
Critical Role ◽  
Terminal Segment ◽  
The Other ◽  
Eukaryotic Cells ◽  
Peptide Substrate ◽  
Family Function ◽  
Aaa Atpase ◽  
Protein Substrates ◽  
Tyrosine Residues ◽  
Microtubule Severing

Many members of the AAA+ ATPase family function as hexamers that unfold their protein substrates. These AAA unfoldases include spastin, which plays a critical role in the architecture of eukaryotic cells by driving the remodeling and severing of microtubules, which are cytoskeletal polymers of tubulin subunits. Here, we demonstrate that a human spastin binds weakly to unmodified peptides from the C-terminal segment of human tubulin α1A/B. A peptide comprising alternating glutamate and tyrosine residues binds more tightly, which is consistent with the known importance of glutamylation for spastin microtubule severing activity. A cryo-EM structure of the spastin-peptide complex at 4.2 Å resolution revealed an asymmetric hexamer in which five spastin subunits adopt a helical, spiral staircase configuration that binds the peptide within the central pore, whereas the sixth subunit of the hexamer is displaced from the peptide/substrate, as if transitioning from one end of the helix to the other. This configuration differs from a recently published structure of spastin from Drosophila melanogaster, which forms a six-subunit spiral without a transitioning subunit. Our structure resembles other recently reported AAA unfoldases, including the meiotic clade relative Vps4, and supports a model in which spastin utilizes a hand-over-hand mechanism of tubulin translocation and microtubule remodeling.

scholarly journals Phosphorylation of the microtubule-severing AAA+ enzyme Katanin regulates C. elegans embryo development

2020 ◽  
Vol 219 (6) ◽  
Author(s):  
Nicolas Joly ◽  
Eva Beaumale ◽  
Lucie Van Hove ◽  
Lisa Martino ◽  
Lionel Pintard
Keyword(s):  
Mitotic Spindle ◽  
The Other ◽  
Meiotic Spindle ◽  
Aaa Atpase ◽  
C Elegans ◽  
Microtubule Severing ◽  
Evolutionarily Conserved ◽  
Necessary And Sufficient ◽  
Fine Tune

The evolutionarily conserved microtubule (MT)-severing AAA-ATPase enzyme Katanin is emerging as a critical regulator of MT dynamics. In Caenorhabditis elegans, Katanin MT-severing activity is essential for meiotic spindle assembly but is toxic for the mitotic spindle. Here we analyzed Katanin dynamics in C. elegans and deciphered the role of Katanin phosphorylation in the regulation of its activity and stability. Katanin is abundant in oocytes, and its levels drop after meiosis, but unexpectedly, a significant fraction is present throughout embryogenesis, where it is dynamically recruited to the centrosomes and chromosomes during mitosis. We show that the minibrain kinase MBK-2, which is activated during meiosis, phosphorylates Katanin at multiple serines. We demonstrate unequivocally that Katanin phosphorylation at a single residue is necessary and sufficient to target Katanin for proteasomal degradation after meiosis, whereas phosphorylation at the other sites only inhibits Katanin ATPase activity stimulated by MTs. Our findings suggest that cycles of phosphorylation and dephosphorylation fine-tune Katanin level and activity to deliver the appropriate MT-severing activity during development.

scholarly journals Calmodulin: A Multitasking Protein in Kv7.2 Potassium Channel Functions

Biomolecules ◽  
2018 ◽  
Vol 8 (3) ◽  
pp. 57 ◽  
Author(s):  
Alessandro Alaimo ◽  
Alvaro Villarroel
Keyword(s):  
Ion Channels ◽  
Potassium Channel ◽  
Critical Role ◽  
The Other ◽  
Eukaryotic Cells ◽  
Calcium Signals ◽  
Voltage Gated ◽  
Cellular Processes ◽  
Cam Regulation

The ubiquitous calcium transducer calmodulin (CaM) plays a pivotal role in many cellular processes, regulating a myriad of structurally different target proteins. Indeed, it is unquestionable that CaM is the most relevant transductor of calcium signals in eukaryotic cells. During the last two decades, different studies have demonstrated that CaM mediates the modulation of several ion channels. Among others, it has been indicated that Kv7.2 channels, one of the members of the voltage gated potassium channel family that plays a critical role in brain excitability, requires CaM binding to regulate the different mechanisms that govern its functions. The purpose of this review is to provide an overview of the most recent advances in structure–function studies on the role of CaM regulation of Kv7.2 and the other members of the Kv7 family.

Beyond the Reward Pathway: Coding Reward Magnitude and Error in the Rat Subthalamic Nucleus

2009 ◽  
Vol 102 (4) ◽  
pp. 2526-2537 ◽  
Author(s):  
Sylvie Lardeux ◽  
Remy Pernaud ◽  
Dany Paleressompoulle ◽  
Christelle Baunez
Keyword(s):  
Subthalamic Nucleus ◽  
Firing Pattern ◽  
Sucrose Solution ◽  
Critical Role ◽  
The Other ◽  
Reward Circuitry ◽  
Reward Delivery ◽  
Reward Pathway ◽  
Subthalamic Neurons ◽  
The Brain

It was recently shown that subthalamic nucleus (STN) lesions affect motivation for food, cocaine, and alcohol, differentially, according to either the nature of the reward or the preference for it. The STN may thus code a reward according to its value. Here, we investigated how the firing of subthalamic neurons is modulated during expectation of a predicted reward between two possibilities (4 or 32% sucrose solution). The firing pattern of neurons responding to predictive cues and to reward delivery indicates that STN neurons can be divided into subpopulations responding specifically to one reward and less or giving no response to the other. In addition, some neurons (“oops” neurons) specifically encode errors as they respond only during error trials. These results reveal that the STN plays a critical role in ascertaining the value of the reward and seems to encode that value differently depending on the magnitude of the reward. These data highlight the importance of the STN in the reward circuitry of the brain.

scholarly journals Nonstructural Protein NP1 of Human Bocavirus 1 Plays a Critical Role in the Expression of Viral Capsid Proteins

2016 ◽  
Vol 90 (9) ◽  
pp. 4658-4669 ◽  
Author(s):  
Wei Zou ◽  
Fang Cheng ◽  
Weiran Shen ◽  
John F. Engelhardt ◽  
Ziying Yan ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Capsid Protein ◽  
Nonstructural Protein ◽  
Critical Role ◽  
The Other ◽  
Capsid Proteins ◽  
Viral Capsid ◽  
Human Bocavirus ◽  
Human Airway ◽  
Viral Capsid Proteins

ABSTRACTA novel chimeric parvoviral vector, rAAV2/HBoV1, in which the recombinant adeno-associated virus 2 (rAAV2) genome is pseudopackaged by the human bocavirus 1 (HBoV1) capsid, has been shown to be highly efficient in gene delivery to human airway epithelia (Z. Yan et al., Mol Ther 21:2181–2194, 2013,http://dx.doi.org/10.1038/mt.2013.92). In this vector production system, we used an HBoV1 packaging plasmid, pHBoV1NSCap, that harbors HBoV1 nonstructural protein (NS) and capsid protein (Cap) genes. In order to simplify this packaging plasmid, we investigated the involvement of the HBoV1 NS proteins in capsid protein expression. We found that NP1, a small NS protein encoded by the middle open reading frame, is required for the expression of the viral capsid proteins (VP1, VP2, and VP3). We also found that the other NS proteins (NS1, NS2, NS3, and NS4) are not required for the expression of VP proteins. We performed systematic analyses of the HBoV1 mRNAs transcribed from the pHBoV1NSCap packaging plasmid and its derivatives in HEK 293 cells. Mechanistically, we found that NP1 is required for both the splicing and the read-through of the proximal polyadenylation site of the HBoV1 precursor mRNA, essential functions for the maturation of capsid protein-encoding mRNA. Thus, our study provides a unique example of how a small viral nonstructural protein facilitates the multifaceted regulation of capsid gene expression.IMPORTANCEA novel chimeric parvoviral vector, rAAV2/HBoV1, expressing a full-length cystic fibrosis transmembrane conductance regulator (CFTR) gene, is capable of correcting CFTR-dependent chloride transport in cystic fibrosis human airway epithelium. Previously, an HBoV1 nonstructural and capsid protein-expressing plasmid, pHBoV1NSCap, was used to package the rAAV2/HBoV1 vector, but yields remained low. In this study, we demonstrated that the nonstructural protein NP1 is required for the expression of capsid proteins. However, we found that the other four nonstructural proteins (NS1 to -4) are not required for expression of capsid proteins. By mutating theciselements that function as internal polyadenylation signals in the capsid protein-expressing mRNA, we constructed a simple HBoV1 capsid protein-expressing gene that expresses capsid proteins as efficiently as pHBoV1NSCap does, and at similar ratios, but independently of NP1. Our study provides a foundation to develop a better packaging system for rAAV2/HBoV1 vector production.

Eternal Guests, Mimics, and Dönme: The Place of German and Turkish Jews in Modern Turkey

2007 ◽  
Vol 37 ◽  
pp. 5-30 ◽  
Author(s):  
Kader Konuk
Keyword(s):  
Critical Role ◽  
The Other ◽  
Turkish Republic ◽  
German Jews ◽  
Other Hand ◽  
Turkish Culture ◽  
The Status ◽  
Modern Turkey ◽  
The One ◽  
European Civilization

AbstractThe place of Jews was highly ambiguous in the newly founded Turkish Republic: In 1928 an assimilationist campaign was launched against Turkish Jews, while only a few years later, in 1933, German scholars—many of them Jewish—were taken in so as to help Europeanize the nation. Turkish authorities regarded the emigrants as representatives of European civilization and appointed scholars like Erich Auerbach to prestigious academic positions that were vital for redefining the humanities in Turkey. This article explores the country's twofold assimilationist policies. On the one hand, Turkey required of its citizens—regardless of ethnic or religious origins—that they conform to a unified Turkish culture; on the other hand, an equally assimilationist modernization project was designed to achieve cultural recognition from the heart of Europe. By linking historical and contemporary discourses, this article shows how tropes of Jewishness have played—and continue to play—a critical role in the conception of Turkish nationhood. The status of Erich Auerbach, Chair of the Faculty for Western Languages and Literatures at İstanbul University from 1936 to 1947, is central to this investigation into the place of Turkish and German Jews in modern Turkey.

scholarly journals Novel Interactions of ESCRT-III with LIP5 and VPS4 and their Implications for ESCRT-III Disassembly

2008 ◽  
Vol 19 (6) ◽  
pp. 2661-2672 ◽  
Author(s):  
Soomin Shim ◽  
Samuel A. Merrill ◽  
Phyllis I. Hanson
Keyword(s):  
Atpase Activity ◽  
Binding Site ◽  
Binding Sites ◽  
Essential Role ◽  
Multivesicular Body ◽  
The Other ◽  
Aaa Atpase ◽  
Direct Binding ◽  
Novel Interactions

The AAA+ ATPase VPS4 plays an essential role in multivesicular body biogenesis and is thought to act by disassembling ESCRT-III complexes. VPS4 oligomerization and ATPase activity are promoted by binding to LIP5. LIP5 also binds to the ESCRT-III like protein CHMP5/hVps60, but how this affects its function remains unclear. Here we confirm that LIP5 binds tightly to CHMP5, but also find that it binds well to additional ESCRT-III proteins including CHMP1B, CHMP2A/hVps2–1, and CHMP3/hVps24 but not CHMP4A/hSnf7–1 or CHMP6/hVps20. LIP5 binds to a different region within CHMP5 than within the other ESCRT-III proteins. In CHMP1B and CHMP2A, its binding site encompasses sequences at the proteins' extreme C-termini that overlap with “MIT interacting motifs” (MIMs) known to bind to VPS4. We find unexpected evidence of a second conserved binding site for VPS4 in CHMP2A and CHMP1B, suggesting that LIP5 and VPS4 may bind simultaneously to these proteins despite the overlap in their primary binding sites. Finally, LIP5 binds preferentially to soluble CHMP5 but instead to polymerized CHMP2A, suggesting that the newly defined interactions between LIP5 and ESCRT-III proteins may be regulated by ESCRT-III conformation. These studies point to a role for direct binding between LIP5 and ESCRT-III proteins that is likely to complement LIP5's previously described ability to regulate VPS4 activity.

Cellular Samurai: katanin and the severing of microtubules

2000 ◽  
Vol 113 (16) ◽  
pp. 2821-2827 ◽  
Author(s):  
L. Quarmby
Keyword(s):  
Epithelial Cells ◽  
Essential Role ◽  
Aaa Atpase ◽  
C Elegans ◽  
Microtubule Severing ◽  
Biochemical Studies ◽  
New Evidence

Recent biochemical studies of the AAA ATPase, katanin, provide a foundation for understanding how microtubules might be severed along their length. These in vitro studies are complemented by a series of recent reports of direct in vivo observation of microtubule breakage, which indicate that the in vitro phenomenon of catalysed microtubule severing is likely to be physiological. There is also new evidence that microtubule severing by katanin is important for the production of non-centrosomal microtubules in cells such as neurons and epithelial cells. Although it has been difficult to establish the role of katanin in mitosis, new genetic evidence indicates that a katanin-like protein, MEI-1, plays an essential role in meiosis in C. elegans. Finally, new proteins involved in the severing of axonemal microtubules have been discovered in the deflagellation system of Chlamydomonas.

Verb paradigm in Tomo Kan Dogon: interconnections of polypredicative constructions, grammaticalization, and tonology

2021 ◽  
pp. 252-268
Author(s):  
V. V. Dyachkov ◽  
Keyword(s):  
Critical Role ◽  
The Other ◽  
Anal Ysis ◽  
Syntactic Position ◽  
The Family ◽  
Similar Range ◽  
Tonal Contour ◽  
Relationship Of

The paper deals with the grammaticalization problems in Tomo Kan (Dogon family, Niger-Congo) and, in particular, with the diachronic relationship of polypredicative constructions and TAM markers. Dogon languages are characterized by TAM systems that seem to be dia-chronically unstable since markers with a similar range of meanings go back to different lexi-cal sources in different languages of the family. TAM markers are apparently associated with polypredicative constructions, which are very common in Dogon and preserve some of their morphosyntactic properties. At the same time, Dogon languages are characterized by complex tonal changes triggered not only by phonological context but also by the syntactic position of constituents. These tonal changes, frequently referred to as tonosyntax, accompany the formation of polypredicative constructions and other syntactic phenomena. A thorough inves-tigation of Tomo Kan TAM markers shows their tonosyntactic properties to resemble those of polypredicative constructions. Moreover, assuming that tonosyntax of polypredicative con-structions triggers certain tonal contour overlays, one can account for tonal alternations ob-served in TAM forms which would have been left otherwise unexplained. However, the anal-ysis also reveals that at least two classes of TAM forms must be distinguished in Tomo Kan: one of them inherits the tonosyntax of polypredicative constructions while the other does not. A hypothesis is put forward that the latter class has a different source of grammaticalization and is probably associated with verb stem incorporation rather than with polypredication. Methodologically, the paper shows a critical role of tonology in the analysis of grammaticalization processes in tonal languages.

Cdc28-Clb mitotic kinase negatively regulates bud site assembly in the budding yeast

2001 ◽  
Vol 114 (1) ◽  
pp. 207-218 ◽  
Author(s):  
C.G. Padmashree ◽  
U. Surana
Keyword(s):  
Kinase Activity ◽  
Budding Yeast ◽  
Critical Role ◽  
The Other ◽  
Yeast Saccharomyces Cerevisiae ◽  
Bud Formation ◽  
Temporal Regulation ◽  
Mitotic Kinase ◽  
Cortical Localization ◽  
Bud Site

In the budding yeast Saccharomyces cerevisiae, a prospective mother normally commences the formation of a daughter (the bud) only in the G(1) phase of the cell division cycle. This suggests a strict temporal regulation of the processes that initiate the formation of a new bud. Using cortical localization of bud site components Spa2 and Bni1 as an indicator of bud site assembly, we show that cells assemble a bud site following inactivation of the Cdc28-Clb mitotic kinase but prior to START. Interestingly, an untimely inactivation of the mitotic kinase is sufficient to drive cells to assemble a new bud site inappropriately in G(2) or M phases. The induction of Cdc28/Clb kinase activity in G(1), on the other hand, dramatically reduces a cell's ability to construct an incipient bud site. Our findings strongly suggest that the Cdc28-Clb kinase plays a critical role in the mechanism that restricts the timing of bud formation to the G(1) phase of the cell cycle.

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