scholarly journals ZnJ6 Is a Thylakoid Membrane DnaJ-Like Chaperone with Oxidizing Activity in Chlamydomonas reinhardtii

2021 ◽  
Vol 22 (3) ◽  
pp. 1136
Author(s):  
Richa Amiya ◽  
Michal Shapira
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Thylakoid Membrane ◽  
Disulfide Bonds ◽  
Protein Misfolding ◽  
Elevated Temperatures ◽  
Site Directed Mutagenesis ◽  
In Vivo Experiments ◽  
Reducing Conditions ◽  
Increased Sensitivity

Assembly of photosynthetic complexes is sensitive to changing light intensities, drought and pathogens, each of which induces a redox imbalance that requires the assistance of specific chaperones to maintain protein structure. Here we report a thylakoid membrane-associated DnaJ-like protein, ZnJ6 (Cre06.g251716.t1.2), in Chlamydomonas reinhardtii. The protein has four CXXCX(G)X(G) motifs that form two zinc fingers (ZFs). Site-directed mutagenesis (Cys > Ser) eliminates the ability to bind zinc. An intact ZF is required for ZnJ6 stability at elevated temperatures. Chaperone assays with recombinant ZnJ6 indicate that it has holding and oxidative activities. ZnJ6 is unable to reduce the disulfide bonds of insulin but prevents its aggregation in a reducing environment. It also assists in the reactivation of reduced denatured RNaseA, possibly by its oxidizing activity. ZnJ6 pull-down assays revealed interactions with oxidoreductases, photosynthetic proteins and proteases. In vivo experiments with a C. reinhardtii insertional mutant (∆ZnJ6) indicate enhanced tolerance to oxidative stress but increased sensitivity to heat and reducing conditions. Moreover, ∆ZnJ6 has reduced photosynthetic efficiency shown by the Chlorophyll fluorescence transient. Taken together, we identify a role for this thylakoid-associated DnaJ-like oxidizing chaperone that assists in the prevention of protein misfolding and aggregation, thus contributing to stress endurance, redox maintenance and photosynthetic balance.

scholarly journals ZnJ6 is a DnaJ-like Chaperone with Oxidizing Activity in the Thylakoid Membrane in Chlamydomonas reinhardtii

2020 ◽  
Author(s):  
Richa Amiya ◽  
Michal Shapira
Keyword(s):  
Protein Aggregation ◽  
Chlamydomonas Reinhardtii ◽  
Thylakoid Membrane ◽  
Stress Proteins ◽  
Elevated Temperatures ◽  
Melting Curve ◽  
Binding Domain ◽  
Site Directed Mutagenesis ◽  
Zinc Binding ◽  
Zinc Binding Domain

ABSTRACTAssembly of photosynthetic complexes is sensitive to changes in light intensities, drought, and pathogens that induce a redox imbalance, and require a variety of substrate-specific chaperones to overcome the stress. Proteins with cysteine (C) residues and disulfide bridges are more responsive to the redox changes. This study reports on a thylakoid membrane-associated DnaJ-like protein, ZnJ6 (ZnJ6.g251716.t1.2) in Chlamydomonas reinhardtii. The protein has four CXXCX(G)X(G) motifs that form a functional zinc-binding domain. Site-directed mutagenesis (Cys to Ser) in all the CXXCX(G)X(G) motifs eliminates its zinc-binding ability. In vitro chaperone assays using recombinant ZnJ6 confirm that it is a chaperone that possesses both holding and oxidative refolding activities. Although mutations (Cys to Ser) do not affect the holding activity of ZnJ6, they impair its ability to promote redox-controlled reactivation of reduced and denatured RNaseA, a common substrate protein. The presence of an intact zinc-binding domain is also required for protein stability at elevated temperatures, as suggested by a single spectrum melting curve. Pull-down assays with recombinant ZnJ6 revealed that it interacts with oxidoreductases, photosynthetic proteins (mainly PSI), and proteases. Our in vivo experiments with Chlamydomonas reinhardtii insertional mutants (ΔZnJ6) expressing a low level of ZnJ6, suggested that the mutant is more tolerant to oxidative stress. In contrast, the wild type has better protection at elevated temperature and DTT induced stress. We propose that DnaJ-like chaperone ZnJ6 assists in the prevention of protein aggregation, stress endurance, and maintenance of redox balance.One-sentence summaryZnJ6 is a redox-regulated DnaJ-like chaperone associated with the thylakoid membrane and involved in the prevention of protein aggregation and stress endurance.

scholarly journals Spatial quality control bypasses cell-based limitations on proteostasis to promote prion curing

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Courtney L Klaips ◽  
Megan L Hochstrasser ◽  
Christine R Langlois ◽  
Tricia R Serio
Keyword(s):  
Quality Control ◽  
Molecular Chaperone ◽  
Protein Misfolding ◽  
Elevated Temperatures ◽  
Control Factor ◽  
Control Mechanisms ◽  
Cellular Environment ◽  
Effective Activity ◽  
Spatial Quality

The proteostasis network has evolved to support protein folding under normal conditions and to expand this capacity in response to proteotoxic stresses. Nevertheless, many pathogenic states are associated with protein misfolding, revealing in vivo limitations on quality control mechanisms. One contributor to these limitations is the physical characteristics of misfolded proteins, as exemplified by amyloids, which are largely resistant to clearance. However, other limitations imposed by the cellular environment are poorly understood. To identify cell-based restrictions on proteostasis capacity, we determined the mechanism by which thermal stress cures the [PSI+]/Sup35 prion. Remarkably, Sup35 amyloid is disassembled at elevated temperatures by the molecular chaperone Hsp104. This process requires Hsp104 engagement with heat-induced non-prion aggregates in late cell-cycle stage cells, which promotes its asymmetric retention and thereby effective activity. Thus, cell division imposes a potent limitation on proteostasis capacity that can be bypassed by the spatial engagement of a quality control factor.

scholarly journals Disulfide-Mediated Oligomer Formation in Borrelia burgdorferi Outer Surface Protein C, a Critical Virulence Factor and Potential Lyme Disease Vaccine Candidate

2011 ◽  
Vol 18 (6) ◽  
pp. 901-906 ◽  
Author(s):  
Christopher G. Earnhart ◽  
DeLacy V. L. Rhodes ◽  
Richard T. Marconi
Keyword(s):  
Lyme Disease ◽  
Borrelia Burgdorferi ◽  
Disulfide Bonds ◽  
Vaccine Candidate ◽  
Site Directed Mutagenesis ◽  
Yield Strain ◽  
Content Type ◽  
Oligomer Formation ◽  
Lyme Disease Vaccine

ABSTRACTBorrelia burgdorferiOspC is an outer membrane lipoprotein required for the establishment of infection in mammals. Due to its universal distribution amongB. burgdorferisensu lato strains and high antigenicity, it is being explored for the development of a next-generation Lyme disease vaccine. An understanding of the surface presentation of OspC will facilitate efforts to maximize its potential as a vaccine candidate. OspC forms homodimers at the cell surface, and it has been hypothesized that it may also form oligomeric arrays. Here, we employ site-directed mutagenesis to test the hypothesis that interdimeric disulfide bonds at cysteine 130 (C130) mediate oligomerization.B. burgdorferiB31ospCwas replaced with a C130A substitution mutant to yield strain B31::ospC(C130A). Recombinant protein was also generated. Disulfide-bond-dependent oligomer formation was demonstrated and determined to be dependent on C130. Oligomerization was not required forin vivofunction, as B31::ospC(C130A) retained infectivity and disseminated normally. The total IgG response and the induced isotype pattern were similar between mice infected with untransformed B31 and those infected with the B31::ospC(C130A) strain. These data indicate that the immune response to OspC is not significantly altered by formation of OspC oligomers, a finding that has significant implications in Lyme disease vaccine design.

scholarly journals LHCSR1 induces a fast and reversible pH-dependent fluorescence quenching in LHCII in Chlamydomonas reinhardtii cells

2016 ◽  
Vol 113 (27) ◽  
pp. 7673-7678 ◽  
Author(s):  
Emine Dinc ◽  
Lijin Tian ◽  
Laura M. Roy ◽  
Robyn Roth ◽  
Ursula Goodenough ◽  
...  
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Light Harvesting ◽  
Ph Sensor ◽  
Complex Stress ◽  
Minimal Cell ◽  
Light Harvesting Complex ◽  
In Vivo Experiments ◽  
Ph Dependent

To avoid photodamage, photosynthetic organisms are able to thermally dissipate the energy absorbed in excess in a process known as nonphotochemical quenching (NPQ). Although NPQ has been studied extensively, the major players and the mechanism of quenching remain debated. This is a result of the difficulty in extracting molecular information from in vivo experiments and the absence of a validation system for in vitro experiments. Here, we have created a minimal cell of the green alga Chlamydomonas reinhardtii that is able to undergo NPQ. We show that LHCII, the main light harvesting complex of algae, cannot switch to a quenched conformation in response to pH changes by itself. Instead, a small amount of the protein LHCSR1 (light-harvesting complex stress related 1) is able to induce a large, fast, and reversible pH-dependent quenching in an LHCII-containing membrane. These results strongly suggest that LHCSR1 acts as pH sensor and that it modulates the excited state lifetimes of a large array of LHCII, also explaining the NPQ observed in the LHCSR3-less mutant. The possible quenching mechanisms are discussed.

scholarly journals On the substrate recognition and negative regulation of SPAK, a kinase modulating Na+-K+-2Cl− cotransport activity

2010 ◽  
Vol 299 (3) ◽  
pp. C614-C620 ◽  
Author(s):  
Kenneth B. Gagnon ◽  
Eric Delpire
Keyword(s):  
Amino Acids ◽  
Aspartic Acid ◽  
Catalytic Domain ◽  
Substrate Recognition ◽  
Site Directed Mutagenesis ◽  
Xenopus Laevis Oocytes ◽  
Threonine Residue ◽  
In Vivo Experiments ◽  
Constitutively Active

Threonines targeted by Ste20-related proline-alanine-rich kinase (SPAK) for phosphorylation have been identified in Na+-K+-2Cl− cotransporter type 1 (NKCC1), NKCC2, and Na+-Cl− cotransporter (NCC). However, what constitutes the substrate recognition of the kinase is still unknown. Using site-directed mutagenesis and functional measurement of NKCC1 activity in Xenopus laevis oocytes, we determined that SPAK recognizes two threonine residues separated by four amino acids. Addition or removal of a single residue abrogated SPAK activation of NKCC1. Although both threonines are followed by hydrophobic residues, in vivo experiments have determined that SPAK activation of the cotransporter only requires a hydrophobic residue after the first threonine. Interestingly, downstream of the second threonine residue, we have identified a conserved aspartic acid residue which is critical for NKCC1 function. Mouse SPAK activity requires phosphorylation of two specific residues by WNK [with no lysine (K)] kinases: a threonine (T243) in the catalytic domain and a serine (S383) in the regulatory domain. We found that mutating the threonine residue into a glutamic acid (T243E) combined with mutation of the serine into an aspartic acid (S383D) rendered SPAK constitutively active. Surprisingly, alanine substitution of S383 or mutation of residues surrounding this residue also resulted in a constitutively active kinase. Interestingly, deletion of amino acids 356–398 identified another serine residue in the catalytic domain (S321) as another putative target of WNK phosphorylation. We found that WNK4 is capable of stimulating the deletion mutant when S321 is present, but not when S321 is mutated into an alanine.

Glucose uptake and glycogen synthesis in normal and chronically active muscles

1993 ◽  
Vol 264 (3) ◽  
pp. E328-E333
Author(s):  
R. J. Talmadge ◽  
H. Silverman
Keyword(s):  
Glucose Uptake ◽  
Contractile Activity ◽  
Glycogen Synthesis ◽  
Diaphragm Muscle ◽  
In Vivo Experiments ◽  
Hindlimb Muscles ◽  
Increased Sensitivity ◽  
And Control

The hindlimb muscles of the C57Bl6J dy2J/dy2J (dy2J) mouse suffer from a chronic neural stimulation (pseudomyotonia), resulting in increased contractile activity. In response to the increased contractile activity, these muscles store increased amounts of glycogen. In this study, glucose uptake and glycogenesis (glycogen synthesis from glucose) were analyzed in chronically active and normal muscles. In vivo experiments demonstrate increased 3-O-methylglucose (3-MG) uptake rates and glycogenesis by chronically active dy2J gastrocnemius muscles (Gast) vs. normal control Gast. The chronically active diaphragm muscle (Dia) showed the highest rates of 3-MG uptake, as well as glycogenesis in vivo when compared with other skeletal muscles. No differences were observed between dy2J and control Dia. The levels of blood glucose were similar between dy2J and control animals. In vitro experiments demonstrated an increased sensitivity and responsiveness to insulin for glucose uptake in the dy2J soleus muscle (Sol). Glycogenesis by dy2J Sol was elevated only at the highest insulin concentration tested (10,000 microU/ml). In contrast, the dy2J extensor digitorum longus muscle had an increased sensitivity and responsiveness to insulin for both glucose uptake and glycogenesis. This study demonstrates that chronically active muscles have elevated capacities for glucose uptake and glycogenesis and may help to explain the elevated glycogen levels in the dy2J hindlimb muscles.

scholarly journals Periodic variations in the ratio of free to thylakoid-bound chloroplast ribosomes during the cell cycle of Chlamydomonas reinhardtii.

1976 ◽  
Vol 71 (2) ◽  
pp. 497-514 ◽  
Author(s):  
N H Chua ◽  
G Blobel ◽  
P Siekevitz ◽  
G E Palade
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Chlorophyll Content ◽  
Thylakoid Membrane ◽  
Mrna Translation ◽  
Chain Elongation ◽  
Slow Cooling ◽  
Membrane Complex ◽  
Thylakoid Membrane Proteins ◽  
Chloroplast Stroma

The ratio of free to thylakoid-bound chloroplast ribosomes in Chlamydomonas reinhardtii undergoes periodic changes during the synchronous light-dark cycle. In the light, when there is an increase in the chlorophyll content and synthesis of thylakoid membrane proteins, about 20-30% of the chloroplast ribosomes are bound to the thylakoid membranes. On the other hand, only a few or no bound ribosomes are present in the dark when there is no increase in the chlorophyll content. The ribosome-membrane interaction depends not only on the developmental stage of the cell but also on light. Thus, bound ribosomes were converted to the free variety after cultures at 4 h in the light had been transferred to the dark for 10 min. Conversely, a larger number of chloroplast ribosomes became attached to the membranes after cultures at 4 h in the dark had been illuminated for 10 min. Under normal conditions, when there was slow cooling of the cultures during cell harvesting, chloroplast polysomal runoff occurred in vivo leading to low levels of thylakoid-bound ribosomes. This polysomal runoff could be arrested by either rapid cooling of the cells or the addition of chloramphenicol or erythromycin. Each of these treatments prevented polypeptide chain elongation on chloroplast ribosomes and thus allowed the polyosomes to remain bound to the thylakoids. Addition of lincomycin, an inhibitor of chain initiation on 70S ribosomes, inhibited the assembly of polysome-thylakoid membrane complex in the light. These results support a model in which initiation of mRNA translation begins in the chloroplast stroma, and the polysome subsequently becomes attached to the thylakoid membrane. Upon natural chain termination, the chloroplast ribosomes are released from the membrane into the stroma.

scholarly journals Construction of Highly Stable Cytotoxic Nuclear-Directed Ribonucleases

Molecules ◽  
2018 ◽  
Vol 23 (12) ◽  
pp. 3273 ◽  
Author(s):  
David Roura Padrosa ◽  
Jessica Castro ◽  
Alejandro Romero-Casañas ◽  
Marc Ribó ◽  
Maria Vilanova ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Tumor Cells ◽  
Disulfide Bonds ◽  
Site Directed Mutagenesis ◽  
Proteinase K ◽  
Human Sera ◽  
Localization Signal ◽  
Cytotoxic Proteins ◽  
Thermal Stability Of

Ribonucleases are proteins whose use is promising in anticancer therapy. We have previously constructed different human pancreatic ribonuclease variants that are selectively cytotoxic for tumor cells by introducing a nuclear localization signal into their sequence. However, these modifications produced an important decrease in their stability compromising their behavior in vivo. Here, we show that we can significantly increase the thermal stability of these cytotoxic proteins by introducing additional disulfide bonds by site-directed mutagenesis. One of these variants increases its thermal stability by around 17 °C, without affecting its catalytic activity while maintaining the cytotoxic activity against tumor cells. We also show that the most stable variant is significantly more resistant to proteolysis when incubated with proteinase K or with human sera, suggesting that its half-live could be increased in vivo once administered.

scholarly journals A chitosan-based cascade-responsive drug delivery system for triple-negative breast cancer therapy

2019 ◽  
Vol 17 (1) ◽  
Author(s):  
Shiwei Niu ◽  
Gareth R. Williams ◽  
Jianrong Wu ◽  
Junzi Wu ◽  
Xuejing Zhang ◽  
...  
Keyword(s):  
Tumor Volume ◽  
Triple Negative ◽  
Elevated Temperatures ◽  
Aqueous Media ◽  
Breast Cancer Therapy ◽  
In Vivo Experiments ◽  
Targeted Treatments ◽  
Cancerous Cells

Abstract Background It is extremely difficult to develop targeted treatments for triple-negative breast (TNB) cancer, because these cells do not express any of the key biomarkers usually exploited for this goal. Results In this work, we develop a solution in the form of a cascade responsive nanoplatform based on thermo-sensitive poly(N-vinylcaprolactam) (PNVCL)-chitosan (CS) nanoparticles (NPs). These are further modified with the cell penetrating peptide (CPP) and loaded with the chemotherapeutic drug doxorubicin (DOX). The base copolymer was optimized to undergo a phase change at the elevated temperatures of the tumor microenvironment. The acid-responsive properties of CS provide a second trigger for drug release, and the inclusion of CPP should ensure the formulations accumulate in cancerous tissue. The resultant CPP-CS-co-PNVCL NPs could self-assemble in aqueous media into spherical NPs of size < 200 nm and with low polydispersity. They are able to accommodate a high DOX loading (14.8% w/w). The NPs are found to be selectively taken up by cancerous cells both in vitro and in vivo, and result in less off-target cytotoxicity than treatment with DOX alone. In vivo experiments employing a TNB xenograft mouse model demonstrated a significant reduction in tumor volume and prolonging of life span, with no obvious systemic toxicity. Conclusions The system developed in this work has the potential to provide new therapies for hard-to-treat cancers.

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