Phenylboronic acid modification augments the lysosome escape and antitumor efficacy of a cylindrical polymer brush-based prodrug

Timely lysosome escape is very important for nanomedicines to avoid premature degradation. Herein, we report an exciting finding that phenylboronic acid (PBA) modification can greatly facilitate the lysosome escape of cylindrical polymer brushes (CPBs), and further promote their exocytosis and transcellular transfer. This fundamental finding for the first time reveals that PBA groups improve the tumor penetration of nanomaterials via an active transcytosis mechanism. We speculate that the mechanism of the PBA-enhanced lysosome escape is associated with the specific interactions of the PBA group with the lysosomal membrane proteins and hot shock proteins. The featured advantage of the PBA modification over the known lysosome escape strategies is that it does not cause significant adverse effects on the properties of the CPBs. Furthermore, doxorubicin was conjugated to the PBA-modified CPBs with drug loading content larger than 20%. This CPBs-based prodrug could eradicate the tumors established in mice by multiple intravenous administration.

A conserved ubiquitin- and ESCRT-dependent pathway internalizes human lysosomal membrane proteins for degradation

The lysosome is an essential organelle to recycle cellular materials and maintain nutrient homeostasis, but the mechanism to down-regulate its membrane proteins is poorly understood. In this study, we performed a cycloheximide (CHX) chase assay to measure the half-lives of approximately 30 human lysosomal membrane proteins (LMPs) and identified RNF152 and LAPTM4A as short-lived membrane proteins. The degradation of both proteins is ubiquitin dependent. RNF152 is a transmembrane E3 ligase that ubiquitinates itself, whereas LAPTM4A uses its carboxyl-terminal PY motifs to recruit NEDD4-1 for ubiquitination. After ubiquitination, they are internalized into the lysosome lumen by the endosomal sorting complexes required for transport (ESCRT) machinery for degradation. Strikingly, when ectopically expressed in budding yeast, human RNF152 is still degraded by the vacuole (yeast lysosome) in an ESCRT-dependent manner. Thus, our study uncovered a conserved mechanism to down-regulate lysosome membrane proteins.

A conserved ubiquitin- and ESCRT-dependent pathway to regulate human lysosomal membrane proteins

The lysosome is an essential organelle to recycle cellular materials and maintain nutrient homeostasis, but the mechanism to down-regulate lysosomal membrane proteins is poorly understood. In this study, we developed a cycloheximide chase assay to measure the half-lives of ~30 human lysosomal membrane proteins, and identified RNF152 as a short-lived protein. The degradation of RNF152 depends on ubiquitin and the endosomal sorting complexes required for transport (ESCRT) machinery. Ubiquitinated RNF152 is sorted and internalized by the ESCRT machinery into the lysosomal lumen for degradation. Strikingly, when expressed in budding yeast, human RNF152 is also degraded by the vacuole (yeast lysosome) in an ESCRT-dependent manner. Thus, our study uncovered a conserved mechanism to down-regulate lysosome membrane proteins.

Expression of alpha-synuclein gene and genes of lysosomal membrane proteins and enzymes in Parkinson’s disease associated with mutation in the GBA gene

Мутации в гене, кодирующем лизосомный фермент глюкоцереброзидазу (GBA), являются фактором высокого риска болезни Паркинсона (БП). Остается неясным, почему не у всех носителей мутаций в данном гене в течение жизни развивается БП. Предполагается, что дисфункция мембранных белков и ферментов лизосом может способствовать развитию БП у носителей мутаций в гене GBA. В данном исследовании была оценена экспрессия генов альфа-синуклеина и LAMP2, GLA, GALNS, SCARB2 в CD45+ клетках периферической крови у пациентов с GBA-БП, бессимптомных носителей мутаций в гене GBA (GBA-носителей), а также в у пациентов с БП и в контроле. Выявлена повышенная экспрессия гена альфа-синуклеина на фоне снижения уровня экспрессии генов мембранных белков лизосом (LAMP2, SCARB2) у пациентов с GBA-БП и GBA-носителей, что может свидетельствовать о вовлеченности этих генов в патогенез GBA-БП. Пониженная экспрессия гена LAMP2 может рассматриваться в качестве одного из триггеров развития БП у носителей мутаций в гене GBA. Mutations in the gene GBA that are encoding the lysosomal enzyme glucocerebrosidase are the most common genetic risk factor for PD. Not every carrier of GBA mutations will develop PD. Probably the dysfunction of lysosomal enzymes and membrane proteins may contribute or protect to the development of PD among carriers of GBA mutations. In the current study LAMP2, GLA, GALNS, SCARB2 and alpha-synuclein mRNA levels in CD45+ blood cells were estimated in patients with GBA-associated PD (GBA-PD), non-manifesting GBA carriers(GBA-Carriers), PD patients and controls. This is the first report estimating LAMP2, GLA, GALNS, SCARB2 and alpha-synuclein expressions in CD45+ blood cells in GBA-PD patients and GBA-Carriers. We revealed increased SNCA expression and changing expression of lysosomal genes (LAMP2, GALNS, SCARB2) that may contribute role these genes in pathogenesis of GBA-PD. Decreased of LAMP2 may be considered as trigger of GBA-PD.

The function of lysosomes and their role in Parkinson’s disease

Lysosomes are cellular organelles that are important for the degradation and recycling of various biomolecules. Specialized lysosomal membrane proteins, as well as soluble enzymes, are important for the efficient turn-over of lysosomal substrates. A deficiency in the degradative capacity of lysosomes leads to severe pathologies referred to as lysosomal storage disorders. There is increasing evidence for the importance of lysosomal function in neurodegenerative disorders, including Parkinson’s disease. One reason for this might be the vulnerability of neuronal cells. Since neurons do not undergo further cell division, non-degraded substrates accumulate in aging cells, causing a buildup of toxicity. Recent genomic screenings identified a number of lysosome-associated genes as potential risk factors for Parkinson’s disease, which are discussed in this review. Moreover, it is outlined how targeting lysosomal function might help in developing novel therapeutic strategies.