Fine-tuning of the Hsc70-based Human Protein Disaggregase Machinery by the Distinctive C-terminal Extension of Apg2

Apg2, one of the three cytosolic Hsp110 chaperones in humans, supports reactivation of unordered and ordered protein aggregates by Hsc70 (HspA8). Together with DnaJB1, Apg2 serves to nucleate Hsc70 molecules into sites where productive entropic pulling forces can be developed. During aggregate reactivation, Apg2 performs as a specialized nucleotide exchange factor, but the origin of its specialization is poorly defined. Here we report on the role of the distinctive C-terminal extension present in Apg2 and other metazoan homologs. We found that the first part of this Apg2 subdomain, with propensity to adopt α-helical structure, interacts with the nucleotide binding domain of Hsc70 in a nucleotide-dependent manner, contributing significantly to the stability of the Hsc70:Apg2 complex. Moreover, the second intrinsically disordered segment of Apg2 C-terminal extension plays an important role as a downregulator of nucleotide exchange. An NMR analysis showed that the interaction with Hsc70 nucleotide binding domain modifies the chemical environment of residues located in important functional sites such as the interface between lobe I and II and the nucleotide binding site. Our data indicate that Apg2 C-terminal extension is a fine-tuner of human Hsc70 activity that optimizes the substrate remodeling ability of the chaperone system.     

Confronting the challenges of discovery of novel antibacterial agents

Bacterial resistance is inevitable and is a growing concern. It can be addressed only by discovery and development of new agents. However the discovery and development of new antibacterial agents are at an all time low. This article broadly examines the historical as well as current status of antibacterial discovery and provides some perspective as how to address some of the challenges.     

A new role for PGRP-S (Tag7) in immune defense: lymphocyte migration is induced by a chemoattractant complex of Tag7 with Mts1

PGRP-S (Tag7) is an innate immunity protein involved in the antimicrobial defense systems, both in insects and in mammals. We have previously shown that Tag7 specifically interacts with several proteins, including Hsp70 and the calcium binding protein S100A4 (Mts1), providing a number of novel cellular functions. Here we show that Tag7–Mts1 complex causes chemotactic migration of lymphocytes, with NK cells being a preferred target. Cells of either innate immunity (neutrophils and monocytes) or acquired immunity (CD4⁺ and CD8⁺ lymphocytes) can produce this complex, which confirms the close connection between components of the 2 branches of immune response.     

Coprinopsis asiaticiphlyctidospora sp. nov., an agaric ammonia fungus from Amami and Okinawa,southern Japan

Coprinopsis asiaticiphlyctidospora (Basidiomycota, Psathyrellaceae), is a new Coprinoid ammonia fungus from Amami and Okinawa, Japan. In macro- and micro-morphology, this species is similar to C. phlyctidospora and C. austrophlyctidospora, but differs in having smaller basidiospores and spiny basidiospore ornamentation. Phylogenetic analysis with the nuclear ribosomal internal transcribed spacer (ITS) data also supports this new taxon.     

Cervical screening in Luxembourg: 1990–1999

For quality assurance purposes, the results of the 1990's obtained by the National Cervical Cancer Screening Programme (NCCSP) launched in 1962 were reviewed. The positive cytodiagnosis, the histologically verified in situ and invasive cervical cancers and the mortality rates were reported.     

Do borderline nuclear changes in gynaecological cytlogy constitute a reliable reporting category?

Fourteen laboratories participated in a national slide exchange study to investigate whether borderline nuclear changes (BNC) constitute a reliable reporting category. Slides were submitted by participating laboratories, having achieved a 100% intralaboratory consensus at the primary screener, checker, and medical levels. Sets of seven slides were examined in laboratories for 1 week, and exchanges were undertaken over a 6-month period. Each laboratory was requested to submit three consensus opinions on each slide at the primary screener, checker, and medical levels.
Response patterns for submitted slides achieving a reporting category consensus at the 50 and 80% consensus levels indicated that negative, BNC, and mild dyskaryosis are distinct and comparable categories. Similarly, the two subcategories of BNC with or without human papillomavirus (HPV) are nearly as distinct as the overall BNC category.
The percentage of submitted slides achieving consensus at consensus levels between 50 and 80% produced variable findings with regard to the practical success of the main reporting categories. The negative category was reasonably successful, whereas mild dyskaryosis was consistently poor. Borderline nuclear changes were successful at the 50% consensus level but showed a rapid decline by the 65% consensus level. The reason(s) for this remains speculative but indicates a possible potential of BNC to work successfully with additional training and education.
Reporting practices were not consistent among the laboratories and differences were identified between medical and nonmedical staff. A high use of the BNC category was noted in slides that failed to achieve consensus. A national study assessing all grades of abnormalities would appear essential.     

The effect of the dark interval in intermittent light on thylakoid development: photosynthetic unit formation and light harvesting protein accumulation

Etiolated bean plants were grown in intermittent light with dark intervals of shorter or longer duration, to modulate the rate of chlorophyll accumulation, relative to that of the other thylakoid components formed. We thus produced conditions under which chlorophyll becomes more or less a limiting factor. We then tested whether LHC complexes can be incorporated in the thylakoid. It was found that an equal amount of chlorophyll, formed under the same total irradiation received, may be used for the stabilization of few and large-in-size PS units containing LHC components (short dark-interval intermittent light), or for the stabilization of many and small-in-size PS units with no LHC components (long dark-interval intermittent light). The size of the PS units diminishes as the dark-interval duration is increased, with no further change after 98 minutes. The PSII/cytf ratio remains constant throughout development in intermittent light and equal to that of mature chloroplasts (PSII/cytf = 1) except in the case of very long dark-interval regimes, where about half PSII units per cytf are present. The PSII/PSI ratio was found to be correlated with the PSII unit size (the larger the size, the lower the ratio). The number of PSI units operating on the same electron transfer chain varied depending on the size of the PSII unit (the larger the PSII unit size, the more the PSI units per chain). The results suggest that it is not the chlorophyll content per se which regulates the stabilization of LHC in developing thylakoids and consequently the size of the PS units, but rather the rate by which it is accumulated, relative to that of the other thylakoid components.Abbreviations Chl Chlorophyll - CL Continuous light - CPa the reaction center complex of PSII - CPI the reaction center complex of PSI - CPIa Chlorophyll protein complex containing the CPI and the light harvesting complex of PSI - fr w fresh weight - LDC Light dark cycles - LHC-I Light-harvesting complex of PSI - LHC-II Light harvesting complex of PSII - PS photosystem - PSI photosystem I - PSII photosystem II