scholarly journals Transition of yeast Can1 transporter to the inward-facing state unveils an α-arrestin target sequence promoting its ubiquitylation and endocytosis

2017 ◽  
Vol 28 (21) ◽  
pp. 2819-2832 ◽  
Author(s):  
Christos Gournas ◽  
Elie Saliba ◽  
Eva-Maria Krammer ◽  
Céline Barthelemy ◽  
Martine Prévost ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Control Mechanism ◽  
Molecular Level ◽  
Membrane Transporters ◽  
Signaling Cascades ◽  
Target Sequence ◽  
Target Region ◽  
Substrate Transport ◽  
Common Control ◽  
Amino Acid Permeases

Substrate-transport–elicited endocytosis is a common control mechanism of membrane transporters avoiding excess uptake of external compounds, though poorly understood at the molecular level. In yeast, endocytosis of transporters is triggered by their ubiquitylation mediated by the Rsp5 ubiquitin-ligase, recruited by α-arrestin–family adaptors. We here report that transport-elicited ubiquitylation of the arginine transporter Can1 is promoted by transition to an inward-facing state. This conformational change unveils a region of the N-terminal cytosolic tail targeted by the Art1 α-arrestin, which is activated via the TORC1 kinase complex upon arginine uptake. Can1 mutants altered in the arginine-binding site or a cytosolic tripeptide sequence permanently expose the α-arrestin–targeted region so that Art1 activation via TORC1 is sufficient to trigger their endocytosis. We also provide evidence that substrate-transport elicited endocytosis of other amino acid permeases similarly involves unmasking of a cytosolic Art1-target region coupled to activation of Art1 via TORC1. Our results unravel a mechanism likely involved in regulation of many other transporters by their own substrates. They also support the emerging view that transporter ubiquitylation relies on combinatorial interaction rules such that α-arrestins, stimulated via signaling cascades or in their basal state, recognize transporter regions permanently facing the cytosol or unveiled during transport.

Novel players fine-tune plant trade-offs

2015 ◽  
Vol 58 ◽  
pp. 83-100 ◽  
Author(s):  
Selena Gimenez-Ibanez ◽  
Marta Boter ◽  
Roberto Solano
Keyword(s):  
Ubiquitin Ligase ◽  
Feedback Loop ◽  
Molecular Level ◽  
26S Proteasome ◽  
Signalling Molecules ◽  
Transcriptional Reprogramming ◽  
Trade Offs ◽  
Jaz Proteins ◽  
Regulatory Feedback Loop ◽  
Fine Tune

Jasmonates (JAs) are essential signalling molecules that co-ordinate the plant response to biotic and abiotic challenges, as well as co-ordinating several developmental processes. Huge progress has been made over the last decade in understanding the components and mechanisms that govern JA perception and signalling. The bioactive form of the hormone, (+)-7-iso-jasmonyl-l-isoleucine (JA-Ile), is perceived by the COI1–JAZ co-receptor complex. JASMONATE ZIM DOMAIN (JAZ) proteins also act as direct repressors of transcriptional activators such as MYC2. In the emerging picture of JA-Ile perception and signalling, COI1 operates as an E3 ubiquitin ligase that upon binding of JA-Ile targets JAZ repressors for degradation by the 26S proteasome, thereby derepressing transcription factors such as MYC2, which in turn activate JA-Ile-dependent transcriptional reprogramming. It is noteworthy that MYCs and different spliced variants of the JAZ proteins are involved in a negative regulatory feedback loop, which suggests a model that rapidly turns the transcriptional JA-Ile responses on and off and thereby avoids a detrimental overactivation of the pathway. This chapter highlights the most recent advances in our understanding of JA-Ile signalling, focusing on the latest repertoire of new targets of JAZ proteins to control different sets of JA-Ile-mediated responses, novel mechanisms of negative regulation of JA-Ile signalling, and hormonal cross-talk at the molecular level that ultimately determines plant adaptability and survival.

scholarly journals Analysis of the sex ratio in Bradysia matogrossensis (Diptera, Sciaridae)

2000 ◽  
Vol 23 (1) ◽  
pp. 97-103 ◽  
Author(s):  
Lincoln S. Rocha ◽  
André Luiz P. Perondini
Keyword(s):  
Sex Ratio ◽  
Sex Determination ◽  
X Chromosome ◽  
Control Mechanism ◽  
Sex Ratios ◽  
Laboratory Strain ◽  
Chromosome Elimination ◽  
Common Control ◽  
Males And Females ◽  
Successive Generations

In sciarid flies, the control of sex determination and of the progeny sex ratio is exercised by the parental females, and is based on differential X-chromosome elimination in the initial stages of embryogenesis. In some species, the females produce unisexual progenies (monogenic females) while in others, the progenies consist of males and females (digenic females). The sex ratio of bisexual progenies is variable, and departs considerably from 1:1. Bradysia matogrossensis shows both monogenic and digenic reproduction. In a recently established laboratory strain of this species, 15% of the females were digenic, 10% produced only females, 13% produced only males, and 62% produced progenies with one predominant sex (33% predominantly of female and 29% predominantly male progenies). These progeny sex ratios were maintained in successive generations. Females from female-skewed progenies yielded female- and male-producing daughters in a 1:1 ratio. In contrast, daughters of females from male-skewed progenies produce bisexual or male-skewed progenies. The X-chromosome of B. matogrossensis shows no inversion or other gross aberration. These results suggest that the control of the progeny sex ratio (or differential X-chromosome elimination) involves more than one locus or, at least, more than one pair of alleles. The data also suggest that, in sciarid flies, monogeny and digeny may share a common control mechanism.

scholarly journals A Nucleus-based Quality Control Mechanism for Cytosolic Proteins

2010 ◽  
Vol 21 (13) ◽  
pp. 2117-2127 ◽  
Author(s):  
Rupali Prasad ◽  
Shinichi Kawaguchi ◽  
Davis T.W. Ng
Keyword(s):  
Quality Control ◽  
Control Systems ◽  
Ubiquitin Ligase ◽  
Nuclear Import ◽  
Control Mechanism ◽  
E3 Ubiquitin Ligase ◽  
26S Proteasome ◽  
Cytosolic Proteins ◽  
Hsp70 Chaperone ◽  
Quality Control Mechanism

Intracellular quality control systems monitor protein conformational states. Irreversibly misfolded proteins are cleared through specialized degradation pathways. Their importance is underscored by numerous pathologies caused by aberrant proteins. In the cytosol, where most proteins are synthesized, quality control remains poorly understood. Stress-inducible chaperones and the 26S proteasome are known mediators but how their activities are linked is unclear. To better understand these mechanisms, a panel of model misfolded substrates was analyzed in detail. Surprisingly, their degradation occurs not in the cytosol but in the nucleus. Degradation is dependent on the E3 ubiquitin ligase San1p, known previously to direct the turnover of damaged nuclear proteins. A second E3 enzyme, Ubr1p, augments this activity but is insufficient by itself. San1p and Ubr1p are not required for nuclear import of substrates. Instead, the Hsp70 chaperone system is needed for efficient import and degradation. These data reveal a new function of the nucleus as a compartment central to the quality control of cytosolic proteins.

scholarly journals The Bul1/2 Alpha-Arrestins Promote Ubiquitylation and Endocytosis of the Can1 Permease upon Cycloheximide-Induced TORC1-Hyperactivation

2021 ◽  
Vol 22 (19) ◽  
pp. 10208
Author(s):  
Amalia H. Megarioti ◽  
Cecilia Primo ◽  
George C. Kapetanakis ◽  
Alexandros Athanasopoulos ◽  
Vicky Sophianopoulou ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Ubiquitin Ligase ◽  
Molecular Mechanisms ◽  
Membrane Transporters ◽  
Environmental Cues ◽  
Specific Amino Acid ◽  
Major Mechanism ◽  
N Terminus ◽  
Golgi Network ◽  
Arginine Permease

Selective endocytosis followed by degradation is a major mechanism for downregulating plasma membrane transporters in response to specific environmental cues. In Saccharomyces cerevisiae, this endocytosis is promoted by ubiquitylation catalyzed by the Rsp5 ubiquitin-ligase, targeted to transporters via adaptors of the alpha-arrestin family. However, the molecular mechanisms of this targeting and their control according to conditions remain incompletely understood. In this work, we dissect the molecular mechanisms eliciting the endocytosis of Can1, the arginine permease, in response to cycloheximide-induced TORC1 hyperactivation. We show that cycloheximide promotes Rsp5-dependent Can1 ubiquitylation and endocytosis in a manner dependent on the Bul1/2 alpha-arrestins. Also crucial for this downregulation is a short acidic patch sequence in the N-terminus of Can1 likely acting as a binding site for Bul1/2. The previously reported inhibition by cycloheximide of transporter recycling, from the trans-Golgi network to the plasma membrane, seems to additionally contribute to efficient Can1 downregulation. Our results also indicate that, contrary to the previously described substrate-transport elicited Can1 endocytosis mediated by the Art1 alpha-arrestin, Bul1/2-mediated Can1 ubiquitylation occurs independently of the conformation of the transporter. This study provides further insights into how distinct alpha-arrestins control the ubiquitin-dependent downregulation of a specific amino acid transporter under different conditions.

scholarly journals The SARS-CoV-2 Spike Variant D614G Favors an Open Conformational State

2020 ◽  
Author(s):  
Rachael A. Mansbach ◽  
Srirupa Chakraborty ◽  
Kien Nguyen ◽  
David C. Montefiori ◽  
Bette Korber ◽  
...  
Keyword(s):  
Neutralizing Antibodies ◽  
Molecular Level ◽  
Receptor Binding Domain ◽  
Target Region ◽  
Infected People ◽  
Viral Loads ◽  
Rapid Transition ◽  
Open States ◽  
Insight Into

SummaryThe COVID-19 pandemic underwent a rapid transition with the emergence of a SARS-CoV-2 variant that carried the amino acid substitution D614G in the Spike protein that became globally prevalent. The G-form is both more infectious in vitro and associated with increased viral loads in infected people. To gain insight into the mechanism underlying these distinctive characteristics, we employed multiple replicas of microsecond all-atom simulations to probe the molecular-level impact of this substitution on Spike’s closed and open states. The open state enables Spike interactions with its human cellular receptor, ACE2. Here we show that changes in the inter-protomer energetics due to the D614G substitution favor a higher population of infection-capable (open) states. The inter-protomer interactions between S1 and S2 subunits in the open state of the D-form are asymmetric. This asymmetry is resolved in the G-form due to the release of tensile hydrogen bonds resulting in an increased population of open conformations. Thus, the increased infectivity of the G-form is likely due to a higher rate of profitable binding encounters with the host receptor. It is also predicted to be more neutralization sensitive due to enhanced exposure of the receptor binding domain, a key target region for neutralizing antibodies.

Mutagenesis of Erythropoietin Receptor Cytoplasmic Lysines Uncouples Erythropoietin-Dependent Growth From Downstream Signal Transduction Cascades.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 3611-3611
Author(s):  
Terri D Richmond ◽  
Natasha Matthew ◽  
Dwayne L. Barber
Keyword(s):  
Cell Surface ◽  
Cell Signaling ◽  
Ubiquitin Ligase ◽  
Conflicts Of Interest ◽  
Fetal Liver ◽  
Critical Role ◽  
E3 Ubiquitin Ligase ◽  
Erythropoietin Receptor ◽  
Signaling Cascades ◽  
Dependent Growth

Abstract Abstract 3611 Poster Board III-547 Erythropoietin (EPO) is the primary cytokine regulator of erythropoiesis, stimulating growth, preventing apoptosis, and promoting differentiation of red blood cell progenitors. Fundamental to this action is the ability of EPO to bind to its cognate receptor on the cell surface, the EPO receptor (EPO-R), and activate the primary associated tyrosine kinase, JAK2. The critical importance of EPO, EPO-R and JAK2 to erythropoiesis is demonstrated by the fatal embryonic anemia that develops upon EPO, EPO-R or JAK2 deletion. Erythrocyte production relies heavily on precise control of EPO-mediated cell signaling cascades. The availability of EPO-R to EPO and the activation of subsequent signaling cascades are tightly regulated by the transit of mature EPO-R to the cell surface from the Golgi, and the mechanisms by which the receptor is internalized and down-regulated. Thus, small changes in plasma membrane EPO-R levels may be reflected in the intensity and duration of downstream signaling protein activation. EPO-R is rapidly ubiquitinated and down-regulated from the cell surface upon EPO stimulation. EPO-R ubiquitination relies on more than one E3 ubiquitin ligase, the U-box containing E3 ubiquitin ligase, p33Rul, and the RING finger E3 ubiquitin ligase SCFβTrcp. The discovery that EPO-R is ubiquitinated and degraded by the proteasome and lysosome lead us to examine the role of EPO-R ubiquitination on cell signaling and proliferation. We hypothesized that EPO-R ubiquitination would result in down-regulation of EPO-mediated signaling cascades. This study characterized which lysines determined EPO-R ubiquitination, and assessed the ability of EPO-R lysine mutants to support EPO-mediated signaling and proliferation. Surprisingly, substitution of all EPO-R cytoplasmic lysines (EPO-R K5R) abolished the ability of EPO-R to support EPO-mediated proliferation in BaF3 cells. However, EPO-dependent phosphorylation of EPO-R, AKT, PKB and STAT5 was detected, albeit at reduced levels. While ubiquitination defects commonly prolong receptor signaling, the kinetics of EPO-R K5R-mediated signaling pathways paralleled Ba/F3-EPO-R cells. Mutation of membrane proximal lysines, K256 and K276, resulted in decreased JAK2 phosphorylation and EPO-R phosphorylation and inhibited proliferation at 0.5U/ml EPO. However, the interaction between JAK2 and EPO-R was not affected. In addition, any EPO-R cytoplasmic lysine could support signaling and proliferation at physiologically elevated EPO concentrations demonstrating significant redundancy. The requirement of EPO-R cytoplasmic lysines to promote CFU-E formation is currently being evaluated by introduction of EPO-R mutants into fetal liver cells derived from EPO-R null mice. These results suggest that the EPO-R cytoplasmic lysines play a critical role in transmitting EPO-dependent growth signals within the cell. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Linear Ubiquitination Mediates EGFR-Induced NF-kB Pathway and Tumor Development

2021 ◽  
Author(s):  
Fang Hua ◽  
Wenzhuo Hap ◽  
Lingyan Wang ◽  
Shitao Li
Keyword(s):  
Cell Proliferation ◽  
Ubiquitin Ligase ◽  
Tumor Development ◽  
E3 Ubiquitin Ligase ◽  
Growth Factor Receptor ◽  
Signaling Cascades ◽  
Ubiquitin Ligase Activity ◽  
Signaling Axis ◽  
Epidermal Growth ◽  
Differentiation And Proliferation

Epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase that instigates several signaling cascades, including the NF-kB signaling pathway, to induce cell differentiation and proliferation. Overexpression and mutations of EGFR are found in up to 30% of solid tumors and correlate with a poor prognosis. Although it is known that EGFR-mediated NF-kB activation is involved in tumor development, the signaling axis is not well elucidated. Here, we found that PKP2 and the LUBAC complex were required for EGFR-mediated NF-kB activation. Upon EGF stimulation, EGFR recruited PKP2 to the plasma membrane, and PKP2 bridged HOIP, the catalytic E3 ubiquitin ligase in the LUBAC, to the EGFR complex. The recruitment activated the LUBAC complex and the linear ubiquitination of NEMO, leading to IkB phosphorylation and subsequent NF-kB activation. Furthermore, EGF-induced linear ubiquitination was critical for tumor cell proliferation and tumor development. Knockout of HOIP impaired EGF-induced NF-kB activity and reduced cell proliferation. HOIP knockout also abrogated the growth of A431 epidermal xenograft tumors in nude mice by more than 70%. More importantly, the HOIP inhibitor, HOIPIN-8, inhibited EGFR-mediated NF-kB activation and cell proliferation of A431, MCF-7, and MDA-MB-231 cancer cells. Overall, our study reveals a novel linear ubiquitination signaling axis of EGFR, and perturbation of HOIP E3 ubiquitin ligase activity is potential targeted cancer therapy.

scholarly journals p47 licenses activation of the immune deficiency pathway in the tick Ixodes scapularis

2018 ◽  
Vol 116 (1) ◽  
pp. 205-210 ◽  
Author(s):  
Erin E. McClure Carroll ◽  
Xiaowei Wang ◽  
Dana K. Shaw ◽  
Anya J. O’Neal ◽  
Adela S. Oliva Chávez ◽  
...  
Keyword(s):  
Immune Deficiency ◽  
Ubiquitin Ligase ◽  
Ixodes Scapularis ◽  
Microbial Colonization ◽  
Signaling Cascades ◽  
Regulatory Subunit ◽  
Dependent Manner ◽  
Microbial Infection ◽  
Imd Pathway ◽  
Molecular Rheostat

The E3 ubiquitin ligase X-linked inhibitor of apoptosis (XIAP) acts as a molecular rheostat for the immune deficiency (IMD) pathway of the tick Ixodes scapularis. How XIAP activates the IMD pathway in response to microbial infection remains ill defined. Here, we identified the XIAP enzymatic substrate p47 as a positive regulator of the I. scapularis IMD network. XIAP polyubiquitylates p47 in a lysine 63-dependent manner and interacts with the p47 ubiquitin-like (UBX) module. p47 also binds to Kenny (IKKγ/NEMO), the regulatory subunit of the inhibitor of nuclear factor (NF)- κB kinase complex. Replacement of the amino acid lysine to arginine within the p47 linker region completely abrogated molecular interactions with Kenny. Furthermore, mitigation of p47 transcription levels through RNA interference in I. scapularis limited Kenny accumulation, reduced phosphorylation of IKKβ (IRD5), and impaired cleavage of the NF-κB molecule Relish. Accordingly, disruption of p47 expression increased microbial colonization by the Lyme disease spirochete Borrelia burgdorferi and the rickettsial agent Anaplasma phagocytophilum. Collectively, we highlight the importance of ticks for the elucidation of paradigms in arthropod immunology. Manipulating immune signaling cascades within I. scapularis may lead to innovative approaches to reducing the burden of tick-borne diseases.

scholarly journals KRIBB11 Induces Apoptosis in A172 Glioblastoma Cells via MULE-Dependent Degradation of MCL-1

Molecules ◽  
2021 ◽  
Vol 26 (14) ◽  
pp. 4165
Author(s):  
Kyunghyun Yoo ◽  
Hye-Hyeon Yun ◽  
Soon-Young Jung ◽  
Jeong-Hwa Lee
Keyword(s):  
Ubiquitin Ligase ◽  
Therapeutic Strategy ◽  
Anticancer Agent ◽  
Molecular Level ◽  
Constitutive Activity ◽  
Glioblastoma Cells ◽  
Essential Step ◽  
Apoptotic Protein ◽  
Induction Of Apoptosis ◽  
A172 Glioma Cells

KRIBB11, an HSF1 inhibitor, was shown to sensitize various types of cancer cells to treatment with several anticancer drugs. However, the exclusive effects of KRIBB11 in preventing the growth of glioblastoma cells and the related mechanisms have not been elucidated yet. Herein, we aimed to examine the potential of KRIBB11 as an anticancer agent for glioblastoma. Using MTT and colony formation assays and Western blotting for c-PARP, we demonstrated that KRIBB11 substantially inhibits the growth of A172 glioma cells by inducing apoptosis. At the molecular level, KRIBB11 decreased anti-apoptotic protein MCL-1 levels, which was attributable to the increase in MULE ubiquitin ligase levels. However, the constitutive activity of HSF1 in A172 cells was not influenced by the exclusive treatment with KRIBB11. Additionally, based on cycloheximide chase assay, we found that KRIBB11 markedly retarded the degradation of MULE. In conclusion, stabilization of MULE upon KRIBB11 treatment is apparently an essential step for degradation of MCL-1 and the subsequent induction of apoptosis in A172 cells. Our results have expanded the knowledge on molecular pathways controlled by KRIBB11 and could be potentially effective for developing an inhibitory therapeutic strategy for glioblastoma.

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