Suppressing toxic aggregates: let MIA do it!

Mitochondrial activity is becoming an inherent aspect of cellular protein homeostasis (proteostasis). In this issue, Schlagowski et al (2021) report on the attractive notion that modulating mitochondrial protein import activity stimulates protein aggregate clearance in the cytosol, thereby affecting cytosolic proteostasis and its collapse observed in neurodegenerative diseases.

Cytosolic aggregation of mitochondrial proteins disrupts cellular homeostasis by stimulating the aggregation of other proteins.

Mitochondria are organelles with their own genomes, but they rely on the import of nuclear-encoded proteins that are translated by cytosolic ribosomes. Therefore, it is important to understand whether failures in the mitochondrial uptake of these nuclear-encoded proteins can cause proteotoxic stress and identify response mechanisms that may counteract it. Here, we report that upon impairments in mitochondrial protein import, high-risk precursor and immature forms of mitochondrial proteins form aberrant deposits in the cytosol. These deposits then cause further cytosolic accumulation and consequently aggregation of other mitochondrial proteins and disease-related proteins, including α-synuclein and amyloid ß. This aggregation triggers a cytosolic protein homeostasis imbalance that is accompanied by specific molecular chaperone responses at both the transcriptomic and protein levels. Altogether, our results provide evidence that mitochondrial dysfunction, specifically protein import defects, contributes to impairments in protein homeostasis, thus revealing a possible molecular mechanism by which mitochondria are involved in neurodegenerative diseases.

Mitochondrial control of cellular protein homeostasis.

Mitochondria are involved in several vital functions of the eukaryotic cell. The majority of mitochondrial proteins are coded by nuclear DNA. Constant import of proteins from the cytosol is a prerequisite for the efficient functioning of the organelle. The protein import into mitochondria is mediated by diverse import pathways and is continuously under watch by quality control systems. However, it is often challenged by both internal and external factors, such as oxidative stress or energy shortage. The impaired protein import and biogenesis leads to the accumulation of mitochondrial precursor proteins in the cytosol and activates several stress response pathways. These defense mechanisms engage a network of processes involving transcription, translation, and protein clearance to restore cellular protein homeostasis. In this review, we provide a comprehensive analysis of various factors and processes contributing to mitochondrial stress caused by protein biogenesis failure and summarize the recovery mechanisms employed by the cell.

Structural Basis for the Inhibitory Effects of Ubistatins in the Ubiquitin-Proteasome Pathway.

The discovery of ubistatins, small molecules that impair proteasomal degradation of proteins by directly binding to polyubiquitin, makes ubiquitin itself a potential therapeutic target. Although ubistatins have the potential for drug development and clinical applications, the lack of structural details of ubiquitin-ubistatin interactions has impeded their development. Here, we characterized a panel of new ubistatin derivatives using functional and binding assays. The structures of ubiquitin complexes with ubistatin B and hemi-ubistatin revealed direct interactions with ubiquitin's hydrophobic surface patch and the basic/polar residues surrounding it. Ubistatin B binds ubiquitin and diubiquitin tighter than a high-affinity ubiquitin receptor and shows strong preference for K48 linkages over K11 and K63. Furthermore, ubistatin B shields ubiquitin conjugates from disassembly by a range of deubiquitinases and by the 26S proteasome. Finally, ubistatin B penetrates cancer cells and alters the cellular ubiquitin landscape. These findings highlight versatile properties of ubistatins and have implications for their future development and use in targeting ubiquitin-signaling pathways.

Structure of the Rpn13-Rpn2 complex provides insights for Rpn13 and Uch37 as anticancer targets.

Proteasome-ubiquitin receptor hRpn13/Adrm1 binds and activates deubiquitinating enzyme Uch37/UCHL5 and is targeted by bis-benzylidine piperidone RA190, which restricts cancer growth in mice xenografts. Here, we solve the structure of hRpn13 with a segment of hRpn2 that serves as its proteasome docking site; a proline-rich C-terminal hRpn2 extension stretches across a narrow canyon of the ubiquitin-binding hRpn13 Pru domain blocking an RA190-binding surface. Biophysical analyses in combination with cell-based assays indicate that hRpn13 binds preferentially to hRpn2 and proteasomes over RA190. hRpn13 also exists outside of proteasomes where it may be RA190 sensitive. RA190 does not affect hRpn13 interaction with Uch37, but rather directly binds and inactivates Uch37. hRpn13 deletion from HCT116 cells abrogates RA190-induced accumulation of substrates at proteasomes. We propose that RA190 targets hRpn13 and Uch37 through parallel mechanisms and at proteasomes, RA190-inactivated Uch37 cannot disassemble hRpn13-bound ubiquitin chains.

"The significance of cardiac magnetic resonance imaging in detection and monitoring of the treatment efficacy of heart involvement in eosinophilic granulomatosis with polyangiitis patients".

BACKGROUND: Cardiac magnetic resonance imaging (CMRI) has emerged as a sensitive and non-invasive technique in the evaluation of cardiac lesions in eosinophilic granulomatosis with polyangiitis (EGPA) patients. OBJECTIVES: To evaluate the ability of CMRI to detection and monitoring of the treatment efficacy in EGPA patients with cardiac involvement. METHODS: To the retrospective-prospective study were enrolled 33 cardiac involvement EGPA patients. In 19 of them CMRI at the moment of diagnosis was performed, in 14 - CMRI after treatment was made, when this method was available - in this group the cardiac involvement was based on the clinical findings. All patients were treated with corticosteroids (CSs) and/or cyclophosphamide (CY). In the first group the control CMRI after one year of treatment was performed, but in the second group the time from the end of the treatment to execution of CMRI was 2-5 years. RESULTS: All patients had heart injury in CMRI. Myocardial edema was present in 87.8% cases, 54.5% of patients had perfusion defects and in all - late gadolinium enhancement was observed. Control CMRI was performed in 32 cases. Improvement was observed in 81% of patients - in 11% of them all lesions undergone completely remission and in 35% of them evolution to global fibrosis was found. In 7% of patients stabilization was achieved and in 12% - progression was observed. CONCLUSIONS: CMRI is a sensitive method detecting cardiac lesions in EGPA patients. It helps to detect patients, who need combined therapy and helps evaluate the therapeutic effect.

Myosin VI Contains a Compact Structural Motif that Binds to Ubiquitin Chains.

Myosin VI is critical for cargo trafficking and sorting during early endocytosis and autophagosome maturation, and abnormalities in these processes are linked to cancers, neurodegeneration, deafness, and hypertropic cardiomyopathy. We identify a structured domain in myosin VI, myosin VI ubiquitin-binding domain (MyUb), that binds to ubiquitin chains, especially those linked via K63, K11, and K29. Herein, we solve the solution structure of MyUb and MyUb:K63-linked diubiquitin. MyUb folds as a compact helix-turn-helix-like motif and nestles between the ubiquitins of K63-linked diubiquitin, interacting with distinct surfaces of each. A nine-amino-acid extension at the C-terminal helix (Helix2) of MyUb is required for myosin VI interaction with endocytic and autophagic adaptors. Structure-guided mutations revealed that a functional MyUb is necessary for optineurin interaction. In addition, we found that an isoform-specific helix restricts MyUb binding to ubiquitin chains. This work provides fundamental insights into myosin VI interaction with ubiquitinated cargo and functional adaptors.

Mycobacterium tuberculosis copper-regulated protein SocB is an intrinsically disordered protein that folds upon interaction with a synthetic phospholipid bilayer.

Multiple genes in Mycobacterium tuberculosis (Mtb) are regulated by copper including socAB (small orf induced by copper A and B), which is induced by copper and repressed by RicR (regulated in copper repressor). socA and socB encode hypothetical proteins of 61 and 54 amino acids, respectively. Here, we use biophysical and computational methods to evaluate the SocB structure. We find that SocB lacks evidence for secondary structure, with no thermal cooperative unfolding event, according to circular dichroism measurements. 2D NMR spectra similarly exhibit hallmarks of a disordered structural state, which is also supported by analyzing SocB diffusion. Altogether, these findings suggest that by itself SocB is intrinsically disordered. Interestingly, SocB interacts with a synthetic phospholipid bilayer and becomes helical, which suggests that it may be membrane-associated.

DNA-damage-inducible 1 protein (Ddi1) contains an uncharacteristic ubiquitin-like domain that binds ubiquitin.

Ddi1 belongs to a family of shuttle proteins targeting polyubiquitinated substrates for proteasomal degradation. Unlike the other proteasomal shuttles, Rad23 and Dsk2, Ddi1 remains an enigma: its function is not fully understood and structural properties are poorly characterized. We determined the structure and binding properties of the ubiquitin-like (UBL) and ubiquitin-associated (UBA) domains of Ddi1 from Saccharomyces cerevisiae. We found that while Ddi1UBA forms a characteristic UBA:ubiquitin complex, Ddi1UBL has entirely uncharacteristic binding preferences. Despite having a ubiquitin-like fold, Ddi1UBL does not interact with typical UBL receptors but unexpectedly binds ubiquitin, forming a unique interface mediated by hydrophobic contacts and by salt bridges between oppositely charged residues of Ddi1UBL and ubiquitin. In stark contrast to ubiquitin and other UBLs, the ß-sheet surface of Ddi1UBL is negatively charged and therefore is recognized in a completely different way. The dual functionality of Ddi1UBL, capable of binding both ubiquitin and proteasome, suggests an intriguing mechanism for Ddi1 as a proteasomal shuttle.

[Disseminated pulmonary actinomycosis - an unusual presentation]. / Rzadka manifestacja plucna promienicy w postaci zmian rozsianych.

Actinomycosis is a rare, chronic infectious disease caused by anaerobic Gram-positive bacteria Actinomyces spp. They induces suppurative inflammation in tissues. They live as commensals in the oropharynx, interstitial tract and genital mucosa, causing almost exclusively endogenic infections. Beacause variable clinical course, its chronicity, quite often actinomycosis mimics rather neoplasmatic disease than infection. We present the case of 56-year old male with unusual pulmonary actinomycosis manifestation as bilateral disseminated lung nodules with systemic symptoms, after initial antitubercular treatment. Diagnosis definitely was made of histologic evaluation of lung specimen from surgical biopsy. After 7-month antibacterial treatment we have achived clinical and radiological improvement.

[Severe hypoxemic respiratory insufficiency in a patient with hepato-pulmonary syndrome coexisting with interstitial lung disease of unknown etiology]. / Ciezka hipoksemiczna niewydolnosc oddechowa u chorego z zespolem watrobowo-plucnym i choroba sródmiazszowa pluc o nieznanej etiologii.

The coexistence of the interstitial lung disease and respiratory failure is rarely associated with extrapulmonary pathology. In patients with liver cirrhosis, hypoxemia may develop in the course of hepato-pulmonary syndrome (HPS), but radiological pathology seen in the course of HPS is of vascular origin, and thus typically not classified as interstitial lung disease. We present a patient with severe hypoxemic respiratory insufficiency in whom hepato-pulmonary syndrome coexisted with interstitial lung disease of unknown etiology. The mechanisms of hypoxemia in the course of hepatic diseases and reasons of possible coincidence of lung and hepatic pathology are discussed.

[Allergic bronchopulmonary aspergillosis mimicking lung cancer in patients without bronchial asthma--case report]. / Alergiczna aspergiloza oskrzelowo-plucna imitujaca guz pluca u chorej bez astmy oskrzelowej--opis przypadku.

Allergic bronchopulmonary aspergillosis (ABPA) is a pulmonary disorder characterized by hypersensitivity reaction to Aspergillus, mainly Aspergillus fumigatus with variable radiological findings. The prevalence of ABPA is about 1-2% in patients with asthma and 5-15% in patients with cystic fibrosis. Very infrequently the disease is diagnosed in patients without previous bronchial asthma. The case of 45 year old women has been shown, who was admitted to the hospital with suspicious of lung cancer with hilar lymphadenopathy, without asthma. After examinations ABPA has been diagnosed. After treatment clinical, radiological, serological improvement were observed.

Nonenzymatic assembly of natural polyubiquitin chains of any linkage composition and isotopic labeling scheme.

Polymeric chains made of a small protein ubiquitin act as molecular signals regulating a variety of cellular processes controlling essentially all aspects of eukaryotic biology. Uncovering the mechanisms that allow differently linked polyubiquitin chains to serve as distinct molecular signals requires the ability to make these chains with the native connectivity, defined length, linkage composition, and in sufficient quantities. This, however, has been a major impediment in the ubiquitin field. Here, we present a robust, efficient, and widely accessible method for controlled iterative nonenzymatic assembly of polyubiquitin chains using recombinant ubiquitin monomers as the primary building blocks. This method uses silver-mediated condensation reaction between the C-terminal thioester of one ubiquitin and the ε-amine of a specific lysine on the other ubiquitin. We augment the nonenzymatic approaches developed recently by using removable orthogonal amine-protecting groups, Alloc and Boc. The use of bacterially expressed ubiquitins allows cost-effective isotopic enrichment of any individual monomer in the chain. We demonstrate that our method yields completely natural polyubiquitin chains (free of mutations and linked through native isopeptide bonds) of essentially any desired length, linkage composition, and isotopic labeling scheme, and in milligram quantities. Specifically, we successfully made Lys11-linked di-, tri-, and tetra-ubiquitins, Lys33-linked diubiquitin, and a mixed-linkage Lys33,Lys11-linked triubiquitin. We also demonstrate the ability to obtain, by high-resolution NMR, residue-specific information on ubiquitin units at any desired position in such chains. This method opens up essentially endless possibilities for rigorous structural and functional studies of polyubiquitin signals.

[Disorders with elevated immunoglobulin E levels]. / Choroby i stany przebiegajace z podwyzszonyn stezeniem immunoglobliny E w surowicy.

Immunoglobulin E (IgE) was first described in 1967. It has the lowest serum concentration of all circulating immunoglobulin isotypes. Serum IgE concentration at birth is low and rises until the age of 10-15 years. The increment of serum IgE in children with predisposition to atopic reactions is usually more abrupt. Total serum IgE levels decline from the second to the eight decade of life. Usually, elevated IgE concentration is related to atopic diseases but there are many other disorders combined with elevated serum IgE (for example: infections, neoplasms, immunodeficiency syndromes, skin disorders, inflammatory diseases). The spectrum of diseases combined with serum IgE elevation was presented in the present article.

Organising pneumonia and lung cancer - case report and review of the literature.

Organising pneumonia (OP) is a distinct clinicopathological entity resulting from pulmonary reaction to noxious environmental or endogenous factors, but also idiopathic cases have been noted. Frequently, small foci of OP accompany lung cancer infiltrations. Also OP is sometimes a reaction to radio- or chemotherapy, but it is rarely a predominant lesion in the course of lung cancer. We present the case of 65-year-old patient who presented with fever, dry cough, exertional dyspnoea and pneumonic consolidation in the right lower lobe. Bronchoscopy revealed squamous carcinoma obstructing the right lower bronchi. He was surgically treated, and the right lower lobe was resected. Pathological examination of a specimen revealed only small infiltration of carcinoma cells in the wall of the bronchi and large confluent areas of organising pneumonia. Surgery was a sufficient treatment for both diseases. Six months later he was in good condition without any pulmonary infiltrations. To sum up, a case of endobronchial squamous cell carcinoma in stage T1N0M0 with predominant clinical and radiological signs of OP is presented.

[Pneumatocele during long-lasting observation of hyper IgE patient]. / Pneumatocele w trakcie dlugotrwalej obserwacji chorego na zespól hiper IgE (zespól Hioba)

Hyper IgE syndrome (Job's syndrome) is a rare multiorgan disease characterized by the triad: elevated serum IgE level, recurrent sinopulmonary infections, most often staphylococcal, and cutaneous cold abscesses starting in infancy. We report 21 years old patient with hyper IgE syndrome, diagnosed at age of 6 years on the basis of hyperimmunoglobulinaemia E and recurrent pulmonary and cutaneous infections. Now he was admitted because of pneumonia complicating with pneumatocele, which could not be resolved despite intravenous antibiotics. Surgical intervention was necessary. The postoperative period was complicated by Staphyloccocus aureus sepsis.