Regulation of autophagic proteolysis by the N-recognin SQSTM1/p62 of the N-end rule pathway.

In macroautophagy/autophagy, cargoes are collected by specific receptors, such as SQSTM1/p62 (sequestosome 1), and delivered to phagophores for lysosomal degradation. To date, little is known about how cells modulate SQSTM1 activity and autophagosome biogenesis in response to accumulating cargoes. In this study, we show that SQSTM1 is an N-recognin whose ZZ domain binds N-terminal arginine (Nt-Arg) and other N-degrons (Nt-Lys, Nt-His, Nt-Trp, Nt-Phe, and Nt-Tyr) of the N-end rule pathway. The substrates of SQSTM1 include the endoplasmic reticulum (ER)-residing chaperone HSPA5/GRP78/BiP. Upon N-end rule interaction with the Nt-Arg of arginylated HSPA5 (R-HSPA5), SQSTM1 undergoes self-polymerization via disulfide bonds of Cys residues including Cys113, facilitating cargo collection. In parallel, Nt-Arg-bound SQSTM1 acts as an inducer of autophagosome biogenesis and autophagic flux. Through this dual regulatory mechanism, SQSTM1 plays a key role in the crosstalk between the ubiquitin (Ub)-proteasome system (UPS) and autophagy. Based on these results, we employed 3D-modeling of SQSTM1 and a virtual chemical library to develop small molecule ligands to the ZZ domain of SQSTM1. These autophagy inducers accelerated the autophagic removal of mutant HTT (huntingtin) aggregates. We suggest that SQSTM1 can be exploited as a novel drug target to modulate autophagic processes in pathophysiological conditions.

Small-scale systems for in vivo drug delivery.

Recent developments in the application of micro- and nanosystems for drug administration include a diverse range of new materials and methods. New approaches include the on-demand activation of molecular interactions, novel diffusion-controlled delivery devices, nanostructured 'smart' surfaces and materials, and prospects for coupling drug delivery to sensors and implants. Micro- and nanotechnologies are enabling the design of novel methods such as radio-frequency addressing of individual molecules or the suppression of immune response to a release device. Current challenges include the need to balance the small scale of the devices with the quantities of drugs that are clinically necessary, the requirement for more stable sensor platforms, and the development of methods to evaluate these new materials and devices for safety and efficacy.

p62/SQSTM1/Sequestosome-1 is an N-recognin of the N-end rule pathway which modulates autophagosome biogenesis.

Macroautophagy mediates the selective degradation of proteins and non-proteinaceous cellular constituents. Here, we show that the N-end rule pathway modulates macroautophagy. In this mechanism, the autophagic adapter p62/SQSTM1/Sequestosome-1 is an N-recognin that binds type-1 and type-2 N-terminal degrons (N-degrons), including arginine (Nt-Arg). Both types of N-degrons bind its ZZ domain. By employing three-dimensional modeling, we developed synthetic ligands to p62 ZZ domain. The binding of Nt-Arg and synthetic ligands to ZZ domain facilitates disulfide bond-linked aggregation of p62 and p62 interaction with LC3, leading to the delivery of p62 and its cargoes to the autophagosome. Upon binding to its ligand, p62 acts as a modulator of macroautophagy, inducing autophagosome biogenesis. Through these dual functions, cells can activate p62 and induce selective autophagy upon the accumulation of autophagic cargoes. We also propose that p62 mediates the crosstalk between the ubiquitin-proteasome system and autophagy through its binding Nt-Arg and other N-degrons.Soluble misfolded proteins that fail to be degraded by the ubiquitin proteasome system (UPS) are redirected to autophagy via specific adaptors, such as p62. Here the authors show that p62 recognises N-degrons in these proteins, acting as a N-recognin from the proteolytic N-end rule pathway, and targets these cargos to autophagosomal degradation.

Testing for Individual Differences in the Identification of Chemosignals for Fear and Happy: Phenotypic Super-Detectors, Detectors and Non-Detectors.

Mood odor identification, explicit awareness of mood odor, may be an important emotion skill and part of a complex dual processing system. It has already been shown that mood odors have significant implicit effects, effects that occur without awareness. This study applies methods for examining human individual differences in the identification of chemosignals for fear and happy, important in itself, and a key to understanding the dual processing of emotion in the olfactory system. Axillary mood odors had been collected from 14 male donors during a mood induction task. Pads were collected after 12 and 24 minutes, creating two doses. Sixty -one participants (41 females) identified the mood odor chemosignals. On a single trial, participants identified 2 doses of fear, 2 doses of happy, and a sterile control. There were 15 trials. The first analysis (rtt) showed that the population was phenotypically heterogeneous, not homogeneous, in identification accuracy. It also showed that a minimum of 10 trials was needed for test reliability. The second analysis, Growth Mixture Modeling, found three distinct groups of detectors: (1) 49.49% were consistently accurate super detectors, (2) 32.52% were accurate above chance level detectors, and (3) 17.98% were non-detectors. Bayesian Posterior Analyses showed reliability of groups at or above 98%. No differences related to mood odor valence (fear or happy), dose (collection at 12 or 24 minutes) or gender were found. Implications for further study of genetic differences, learning and function of identification are noted. It appears that many people can be reliable in explicitly identifying fear and happy mood odors but this skill is not homogeneous.