scholarly journals HSBP1 Is a Novel Interactor of FIP200 and ATG13 That Promotes Autophagy Initiation and Picornavirus Replication

2021 ◽  
Vol 11 ◽  
Author(s):  
Mario Mauthe ◽  
Nilima Dinesh Kumar ◽  
Pauline Verlhac ◽  
Nicole van de Beek ◽  
Fulvio Reggiori
Keyword(s):  
Coiled Coil ◽  
Host Factor ◽  
Autophagy Induction ◽  
Cellular Pathways ◽  
The Stability

ATG13 and FIP200 are two subunits of the ULK kinase complex, a key regulatory component of the autophagy machinery. We have previously found that the FIP200-ATG13 subcomplex controls picornavirus replication outside its role in the ULK kinase complex and autophagy. Here, we characterized HSBP1, a very small cytoplasmic coiled-coil protein, as a novel interactor of FIP200 and ATG13 that binds these two proteins via FIP200. HSBP1 is a novel pro-picornaviral host factor since its knockdown or knockout, inhibits the replication of various picornaviruses. The anti-picornaviral function of the FIP200-ATG13 subcomplex was abolished when HSBP1 was depleted, inferring that this subcomplex negatively regulates HSBP1’s pro-picornaviral function during infections. HSBP1depletion also reduces the stability of ULK kinase complex subunits, resulting in an impairment in autophagy induction. Altogether, our data show that HSBP1 interaction with FIP200-ATG13-containing complexes is involved in the regulation of different cellular pathways.

Early signalling events of autophagy

2013 ◽  
Vol 55 ◽  
pp. 1-15 ◽  
Author(s):  
Laura E. Gallagher ◽  
Edmond Y.W. Chan
Keyword(s):  
Protein Kinase ◽  
Focal Adhesion Kinase ◽  
Focal Adhesion ◽  
Mammalian Cells ◽  
Mammalian Target Of Rapamycin ◽  
Interacting Protein ◽  
The Core ◽  
Autophagy Gene ◽  
Autophagy Induction ◽  
Cellular Pathways

Autophagy is a conserved cellular degradative process important for cellular homoeostasis and survival. An early committal step during the initiation of autophagy requires the actions of a protein kinase called ATG1 (autophagy gene 1). In mammalian cells, ATG1 is represented by ULK1 (uncoordinated-51-like kinase 1), which relies on its essential regulatory cofactors mATG13, FIP200 (focal adhesion kinase family-interacting protein 200 kDa) and ATG101. Much evidence indicates that mTORC1 [mechanistic (also known as mammalian) target of rapamycin complex 1] signals downstream to the ULK1 complex to negatively regulate autophagy. In this chapter, we discuss our understanding on how the mTORC1–ULK1 signalling axis drives the initial steps of autophagy induction. We conclude with a summary of our growing appreciation of the additional cellular pathways that interconnect with the core mTORC1–ULK1 signalling module.

scholarly journals TNRC6 proteins modulate hepatitis C virus replication by spatially regulating the binding of miR-122/Ago2 complexes to viral RNA

2019 ◽  
Vol 47 (12) ◽  
pp. 6411-6424 ◽  
Author(s):  
You Li ◽  
Li Wang ◽  
Efraín E Rivera-Serrano ◽  
Xian Chen ◽  
Stanley M Lemon
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Spatial Organization ◽  
Host Factor ◽  
Viral Rna ◽  
Fine Tuning ◽  
Hcv Rna ◽  
Human Hepatoma Cells ◽  
Translational Activity ◽  
The Stability

AbstractThe liver-specific microRNA, miR-122, is an essential host factor for replication of the hepatitis C virus (HCV). miR-122 stabilizes the positive-strand HCV RNA genome and promotes its synthesis by binding two sites (S1 and S2) near its 5′ end in association with Ago2. Ago2 is essential for both host factor activities, but whether other host proteins are involved is unknown. Using an unbiased quantitative proteomics screen, we identified the TNRC6 protein paralogs, TNRC6B and TNRC6C, as functionally important but redundant components of the miR-122/Ago2 host factor complex. Doubly depleting TNRC6B and TNRC6C proteins reduced HCV replication in human hepatoma cells, dampening miR-122 stimulation of viral RNA synthesis without reducing the stability or translational activity of the viral RNA. TNRC6B/C were required for optimal miR-122 host factor activity only when S1 was able to bind miR-122, and restricted replication when S1 was mutated and only S2 bound by miR-122. TNRC6B/C preferentially associated with S1, and TNRC6B/C depletion enhanced Ago2 association at S2. Collectively, these data suggest a model in which TNRC6B/C regulate the assembly of miR-122/Ago complexes on HCV RNA, preferentially directing miR-122/Ago2 to S1 while restricting its association with S2, thereby fine-tuning the spatial organization of miR-122/Ago2 complexes on the viral genome.

scholarly journals Phosphoregulation of tropomyosin is crucial for actin cable turnover and division site placement

2019 ◽  
Vol 218 (11) ◽  
pp. 3548-3559 ◽  
Author(s):  
Saravanan Palani ◽  
Darius V. Köster ◽  
Tomoyuki Hatano ◽  
Anton Kamnev ◽  
Taishi Kanamaru ◽  
...  
Keyword(s):  
Fission Yeast ◽  
Actin Filaments ◽  
Coiled Coil ◽  
Actin Binding ◽  
Division Site ◽  
Actin Cable ◽  
Nonmuscle Cells ◽  
The Stability ◽  
Actin Cables

Tropomyosin is a coiled-coil actin binding protein key to the stability of actin filaments. In muscle cells, tropomyosin is subject to calcium regulation, but its regulation in nonmuscle cells is not understood. Here, we provide evidence that the fission yeast tropomyosin, Cdc8, is regulated by phosphorylation of a serine residue. Failure of phosphorylation leads to an increased number and stability of actin cables and causes misplacement of the division site in certain genetic backgrounds. Phosphorylation of Cdc8 weakens its interaction with actin filaments. Furthermore, we show through in vitro reconstitution that phosphorylation-mediated release of Cdc8 from actin filaments facilitates access of the actin-severing protein Adf1 and subsequent filament disassembly. These studies establish that phosphorylation may be a key mode of regulation of nonmuscle tropomyosins, which in fission yeast controls actin filament stability and division site placement.

616 Specific Amino Acid Mutation of p53 Enhanced the Stability of Intracellular CagA by Inhibiting Autophagy Induction

2012 ◽  
Vol 142 (5) ◽  
pp. S-120-S-121
Author(s):  
Hitoshi Tsugawa ◽  
Hidekazu Suzuki ◽  
Masanori Hatakeyama ◽  
Toshiya Hirayama ◽  
Juntaro Matsuzaki ◽  
...  
Keyword(s):  
Amino Acid ◽  
Amino Acid Mutation ◽  
Specific Amino Acid ◽  
Autophagy Induction ◽  
The Stability

scholarly journals Coiled-Coil Trigger Motifs in the 1B and 2B Rod Domain Segments Are Required for the Stability of Keratin Intermediate Filaments

2000 ◽  
Vol 11 (10) ◽  
pp. 3539-3558 ◽  
Author(s):  
Kenneth C. Wu ◽  
Janine T. Bryan ◽  
Maria I. Morasso ◽  
Shyh-Ing Jang ◽  
Jeung-Hoon Lee ◽  
...  
Keyword(s):  
Coiled Coil ◽  
Coiled Coils ◽  
Detectable Effect ◽  
Keratin 5 ◽  
Molecular Stability ◽  
Potential Trigger ◽  
Helical Proteins ◽  
The Stability

Many α-helical proteins that form two-chain coiled coils possess a 13-residue trigger motif that seems to be required for the stability of the coiled coil. However, as currently defined, the motif is absent from intermediate filament (IF) protein chains, which nevertheless form segmented two-chain coiled coils. In the present work, we have searched for and identified two regions in IF chains that are essential for the stability necessary for the formation of coiled-coil molecules and thus may function as trigger motifs. We made a series of point substitutions with the keratin 5/keratin 14 IF system. Combinations of the wild-type and mutant chains were assembled in vitro and in vivo, and the stabilities of two-chain (one-molecule) and two-molecule assemblies were examined with use of a urea disassembly assay. Our new data document that there is a region located between residues 100 and 113 of the 2B rod domain segment that is absolutely required for molecular stability and IF assembly. This potential trigger motif differs slightly from the consensus in having an Asp residue at position 4 (instead of a Glu) and a Thr residue at position 9 (instead of a charged residue), but there is an absolute requirement for a Glu residue at position 6. Because these 13 residues are highly conserved, it seems possible that this motif functions in all IF chains. Likewise, by testing keratin IF with substitutions in both chains, we identified a second potential trigger motif between residues 79 and 91 of the 1B rod domain segment, which may also be conserved in all IF chains. However, we were unable to find a trigger motif in the 1A rod domain segment. In addition, many other point substitutions had little detectable effect on IF assembly, except for the conserved Lys-23 residue of the 2B rod domain segment. Cross-linking and modeling studies revealed that Lys-23 may lie very close to Glu-106 when two molecules are aligned in the A22 mode. Thus, the Glu-106 residue may have a dual role in IF structure: it may participate in trigger formation to afford special stability to the two-chain coiled-coil molecule, and it may participate in stabilization of the two-molecule hierarchical stage of IF structure.

Transcriptional regulation of the uptake [NiFe]hydrogenase genes in Rhodobacter capsulatus

2005 ◽  
Vol 33 (1) ◽  
pp. 28-32 ◽  
Author(s):  
P.M. Vignais ◽  
S. Elsen ◽  
A. Colbeau
Keyword(s):  
Gene Expression ◽  
Rhodobacter Capsulatus ◽  
Response Regulator ◽  
Regulatory System ◽  
Integration Host Factor ◽  
Host Factor ◽  
Promoter Recognition ◽  
The Stability ◽  
A Site

Transcription of the hupSL genes, which encode the uptake [NiFe]hydrogenase of Rhodobacter capsulatus, is specifically activated by H2. Three proteins are involved, namely the H2-sensor HupUV, the histidine kinase HupT and the transcriptional activator HupR. hupT and hupUV mutants have the same phenotype, i.e. an increased level of hupSL expression (assayed by phupS::lacZ fusion) in the absence of H2; they negatively control hupSL gene expression. HupT can autophosphorylate its conserved His217, and in vitro phosphotransfer to Asp54 of its cognate response regulator, HupR, was demonstrated. The non-phosphorylated form of HupR binds to an enhancer site (5′-TTG-N5-CAA) of phupS localized at −162/−152 nt and requires integration host factor to activate fully hupSL transcription. HupUV is an O2-insensitive [NiFe]hydrogenase, which interacts with HupT to regulate the phosphorylation state of HupT in response to H2 availability. The N-terminal domain of HupT, encompassing the PAS domain, is required for interaction with HupUV. This interaction with HupT, leading to the formation of a (HupT)2–(HupUV)2 complex, is weakened in the presence of H2, but incubation of HupUV with H2 has no effect on the stability of the heterodimer/tetramer, HupUV–(HupUV)2, equilibrium. HupSL biosynthesis is also under the control of the global two-component regulatory system RegB/RegA, which controls gene expression in response to redox. RegA binds to a site close to the −35 promoter recognition site and to a site overlapping the integration host factor DNA-binding site (5′-TCACACACCATTG, centred at −87 nt) and acts as a repressor.

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