scholarly journals Role of KASH domain lengths in the regulation of LINC complexes

2019 ◽  
Vol 30 (16) ◽  
pp. 2076-2086 ◽  
Author(s):  
Zeinab Jahed ◽  
Hongyan Hao ◽  
Vyom Thakkar ◽  
Uyen T. Vu ◽  
Venecia A. Valdez ◽  
...  
Keyword(s):  
The Sun ◽  
Linc Complex ◽  
Cellular Functions ◽  
C Elegans ◽  
Physical Forces ◽  
Domain Protein ◽  
Dynamics Simulations ◽  
Sun Domain

The linker of the nucleoskeleton and cytoskeleton (LINC) complex is formed by the conserved interactions between Sad-1 and UNC-84 (SUN) and Klarsicht, ANC-1, SYNE homology (KASH) domain proteins, providing a physical coupling between the nucleoskeleton and cytoskeleton that mediates the transfer of physical forces across the nuclear envelope. The LINC complex can perform distinct cellular functions by pairing various KASH domain proteins with the same SUN domain protein. For example, in Caenorhabditis elegans, SUN protein UNC-84 binds to two KASH proteins UNC-83 and ANC-1 to mediate nuclear migration and anchorage, respectively. In addition to distinct cytoplasmic domains, the luminal KASH domain also varies among KASH domain proteins of distinct functions. In this study, we combined in vivo C. elegans genetics and in silico molecular dynamics simulations to understand the relation between the length and amino acid composition of the luminal KASH domain, and the function of the SUN–KASH complex. We show that longer KASH domains can withstand and transfer higher forces and interact with the membrane through a conserved membrane proximal EEDY domain that is unique to longer KASH domains. In agreement with our models, our in vivo results show that swapping the KASH domains of ANC-1 and UNC-83, or shortening the KASH domain of ANC-1, both result in a nuclear anchorage defect in C. elegans.

scholarly journals A molecular model for LINC complex regulation: activation of SUN2 for KASH binding

2018 ◽  
Vol 29 (16) ◽  
pp. 2012-2023 ◽  
Author(s):  
Zeinab Jahed ◽  
Uyen T. Vu ◽  
Darya Fadavi ◽  
Huimin Ke ◽  
Akshay Rathish ◽  
...  
Keyword(s):  
Molecular Model ◽  
Gel Filtration ◽  
Coiled Coil ◽  
Molecular Complexes ◽  
The Sun ◽  
Linc Complex ◽  
Structural Details ◽  
Direct Linkage ◽  
Dynamics Simulations ◽  
Sun Domain

Linkers of the nucleoskeleton and cytoskeleton are key molecular complexes that span the nuclear envelope (NE) and provide a direct linkage between the nucleoskeleton and cytoskeleton. Two major components of these complexes are members of the SUN and KASH protein families that interact in the perinuclear space to allow the transmission of mechanochemical signals across the NE. Structural details of the mammalian SUN domain protein SUN2 have established that SUN2 must form a trimer to bind to KASH, and that this trimerization is mediated through two predicted coiled-coil regions of the protein, CC1 and CC2, which precede the SUN domain. Recent crystallographic data suggest that CC2-SUN formed an unexpected autoinhibited monomer unable to bind to KASH. These structural insights raise the question of how full-length SUN2 transitions from a monomer to a trimer inside the NE. In this study we used a computational approach to model a fragment of SUN2 containing CC1, CC2, and the SUN domain. We observed the dynamics of these modeled structures using ∼1 μs molecular dynamics simulations and showed that the interplay between CC1 and CC2 may be sufficient for the release of CC2-SUN2 from its autoinhibited state. Additionally, using our models and gel filtration analysis, we show the involvement of an E452 residue on CC1 in the monomer–­trimer transition of SUN2. Intriguingly, mutations in this residue have been seen in muscular dystrophy–associated SUN2 variants. Finally, we propose a Ca2+-dependent monomer–trimer transition of SUN2.

scholarly journals Sad1 Spatiotemporally Regulates Kinetochore Clustering To Ensure High-Fidelity Chromosome Segregation in the Human Fungal Pathogen Cryptococcus neoformans

mSphere ◽  
2018 ◽  
Vol 3 (4) ◽  
Author(s):  
Vikas Yadav ◽  
Kaustuv Sanyal
Keyword(s):  
Cryptococcus Neoformans ◽  
Chromosome Segregation ◽  
Yeast Species ◽  
Mitotic Cell ◽  
High Fidelity ◽  
The Sun ◽  
Linc Complex ◽  
Content Type ◽  
Sun Domain

ABSTRACT Kinetochore clustering, frequently observed in yeasts, plays a key role in genome organization and chromosome segregation. In the absence of the metaphase plate arrangement, kinetochore clustering in yeast species is believed to facilitate timely kinetochore-microtubule interactions to achieve bivalent attachments of chromosomes during metaphase. The factors determining the dynamics of kinetochore clustering remain largely unknown. We previously reported that kinetochores oscillate between an unclustered and a clustered state during the mitotic cell cycle in the basidiomycetous yeast Cryptococcus neoformans. Based on tubulin localization patterns, while kinetochore clustering appears to be microtubule dependent, an indirect interaction of microtubules with kinetochores is expected in C. neoformans. In this study, we sought to examine possible roles of the SUN-KASH protein complex, known to form a bridge across the nuclear envelope, in regulating kinetochore clustering in C. neoformans. We show that the SUN domain protein Sad1 localizes close to kinetochores in interphase as well as in mitotic cells. Sad1 is nonessential for viability in C. neoformans but is required for proper growth and high-fidelity chromosome segregation. Further, we demonstrate that the onset of kinetochore clustering is significantly delayed in cells lacking Sad1 compared to wild-type cells. Taken together, this study identifies a novel role of the SUN domain protein Sad1 in spatiotemporal regulation of kinetochore clustering during the mitotic cell cycle in C. neoformans. IMPORTANCE The linker of nucleoskeleton and cytoskeleton (LINC) complex is present in fungi, animals, and plants. It performs diverse functions in animals, and its role(s) have recently been explored in plants. In ascomycetous yeast species, the role of the LINC complex in spindle pole body function and telomere clustering during meiosis has been determined. However, nothing is known about the LINC complex in the fungal phylum of Basidiomycota. In this study, we identified the role of the LINC complex in kinetochore dynamics as well as in nuclear migration in a basidiomycetous yeast, Cryptococcus neoformans, a human pathogen. Unlike most other yeast species, kinetochores remain unclustered during interphase but gradually cluster during mitosis in C. neoformans. We report that the LINC complex is required for timely onset of kinetochore clustering and high-fidelity chromosome segregation in C. neoformans. Thus, our study identifies a novel factor required for kinetochore clustering during mitosis in yeast species.

scholarly journals SUNny Ways: The Role of the SUN-Domain Protein Mps3 Bridging Yeast Nuclear Organization and Lipid Homeostasis

2020 ◽  
Vol 11 ◽  
Author(s):  
Maria Laura Sosa Ponce ◽  
Sarah Moradi-Fard ◽  
Vanina Zaremberg ◽  
Jennifer A. Cobb
Keyword(s):  
Nuclear Organization ◽  
Lipid Homeostasis ◽  
The Sun ◽  
Domain Protein ◽  
Sun Domain

scholarly journals Mps2 links Csm4 and Mps3 to form a telomere-associated LINC complex in budding yeast

2020 ◽  
Vol 3 (12) ◽  
pp. e202000824
Author(s):  
Jinbo Fan ◽  
Hui Jin ◽  
Bailey A Koch ◽  
Hong-Guo Yu
Keyword(s):  
Nuclear Membrane ◽  
Meiotic Recombination ◽  
Budding Yeast ◽  
Transmembrane Proteins ◽  
Yeast Cells ◽  
The Sun ◽  
Linc Complex ◽  
Domain Protein ◽  
Yeast Meiosis ◽  
Sun Domain

The linker of the nucleoskeleton and cytoskeleton (LINC) complex is composed of two transmembrane proteins: the KASH domain protein localized to the outer nuclear membrane and the SUN domain protein to the inner nuclear membrane. In budding yeast, the sole SUN domain protein, Mps3, is thought to pair with either Csm4 or Mps2, two KASH-like proteins, to form two separate LINC complexes. Here, we show that Mps2 mediates the interaction between Csm4 and Mps3 to form a heterotrimeric telomere-associated LINC (t-LINC) complex in budding yeast meiosis. Mps2 binds to Csm4 and Mps3, and all three are localized to the telomere. Telomeric localization of Csm4 depends on both Mps2 and Mps3; in contrast, Mps2’s localization depends on Mps3 but not Csm4. Mps2-mediated t-LINC complex regulates telomere movement and meiotic recombination. By ectopically expressing CSM4 in vegetative yeast cells, we reconstitute the heterotrimeric t-LINC complex and demonstrate its ability to tether telomeres. Our findings therefore reveal the heterotrimeric composition of the t-LINC complex in budding yeast and have implications for understanding variant LINC complex formation.

scholarly journals Syndecan Transmembrane Domain Specifically Regulates Downstream Signaling Events of the Transmembrane Receptor Cytoplasmic Domain

2021 ◽  
Vol 22 (15) ◽  
pp. 7918
Author(s):  
Jisun Hwang ◽  
Bohee Jang ◽  
Ayoung Kim ◽  
Yejin Lee ◽  
Joonha Lee ◽  
...  
Keyword(s):  
Transmembrane Domain ◽  
Growth Factor Receptor ◽  
Cytoplasmic Domain ◽  
Nih3t3 Cells ◽  
C Elegans ◽  
Downstream Signaling ◽  
Downstream Effectors ◽  
Signaling Events

Despite the known importance of the transmembrane domain (TMD) of syndecan receptors in cell adhesion and signaling, the molecular basis for syndecan TMD function remains unknown. Using in vivo invertebrate models, we found that mammalian syndecan-2 rescued both the guidance defects in C. elegans hermaphrodite-specific neurons and the impaired development of the midline axons of Drosophila caused by the loss of endogenous syndecan. These compensatory effects, however, were reduced significantly when syndecan-2 dimerization-defective TMD mutants were introduced. To further investigate the role of the TMD, we generated a chimera, 2eTPC, comprising the TMD of syndecan-2 linked to the cytoplasmic domain of platelet-derived growth factor receptor (PDGFR). This chimera exhibited SDS-resistant dimer formation that was lost in the corresponding dimerization-defective syndecan-2 TMD mutant, 2eT(GL)PC. Moreover, 2eTPC specifically enhanced Tyr 579 and Tyr 857 phosphorylation in the PDGFR cytoplasmic domain, while the TMD mutant failed to support such phosphorylation. Finally, 2eTPC, but not 2eT(GL)PC, induced phosphorylation of Src and PI3 kinase (known downstream effectors of Tyr 579 phosphorylation) and promoted Src-mediated migration of NIH3T3 cells. Taken together, these data suggest that the TMD of a syndecan-2 specifically regulates receptor cytoplasmic domain function and subsequent downstream signaling events controlling cell behavior.

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.

scholarly journals Essential Role of Ubiquitin-Specific Protease 8 for Receptor Tyrosine Kinase Stability and Endocytic Trafficking In Vivo

2007 ◽  
Vol 27 (13) ◽  
pp. 5029-5039 ◽  
Author(s):  
Sandra Niendorf ◽  
Alexander Oksche ◽  
Agnes Kisser ◽  
Jürgen Löhler ◽  
Marco Prinz ◽  
...  
Keyword(s):  
Growth Factor ◽  
Tyrosine Kinases ◽  
Growth Regulation ◽  
Growth Factor Receptor ◽  
Deubiquitinating Enzymes ◽  
Cellular Functions ◽  
Early Endosomes ◽  
Immortalized Cells

ABSTRACT Posttranslational modification by ubiquitin controls multiple cellular functions and is counteracted by the activities of deubiquitinating enzymes. UBPy (USP8) is a growth-regulated ubiquitin isopeptidase that interacts with the HRS-STAM complex. Using Cre-loxP-mediated gene targeting in mice, we show that lack of UBPy results in embryonic lethality, whereas its conditional inactivation in adults causes fatal liver failure. The defect is accompanied by a strong reduction or absence of several growth factor receptor tyrosine kinases (RTKs), like epidermal growth factor receptor, hepatocyte growth factor receptor (c-met), and ERBB3. UBPy-deficient cells exhibit aberrantly enlarged early endosomes colocalizing with enhanced ubiquitination and have reduced levels of HRS and STAM2. Congruently immortalized cells gradually stop proliferation upon induced deletion of UBPy. These results unveil a central and nonredundant role of UBPy in growth regulation, endosomal sorting, and the control of RTKs in vivo.

scholarly journals Cleavage of the SUN-domain protein Mps3 at its N-terminus regulates centrosome disjunction in budding yeast meiosis

PLoS Genetics ◽  
2017 ◽  
Vol 13 (6) ◽  
pp. e1006830 ◽  
Author(s):  
Ping Li ◽  
Hui Jin ◽  
Bailey A. Koch ◽  
Rebecca L. Abblett ◽  
Xuemei Han ◽  
...  
Keyword(s):  
Budding Yeast ◽  
The Sun ◽  
N Terminus ◽  
Domain Protein ◽  
Yeast Meiosis ◽  
Sun Domain

scholarly journals Comparative Analysis of Sequence-Structure Function Relationship of the SUN-Domain Protein CaSUN1

2017 ◽  
Vol 05 (03) ◽  
Author(s):  
Poonam Mishra ◽  
Vijay Wardhan ◽  
Aarti Pandey ◽  
Subhra Chakraborty ◽  
Gunjan Garg ◽  
...  
Keyword(s):  
Comparative Analysis ◽  
Structure Function ◽  
The Sun ◽  
Sequence Structure ◽  
Structure Function Relationship ◽  
Domain Protein ◽  
Function Relationship ◽  
Relationship Of ◽  
Sun Domain
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