Learn more: Aggregation and Proteostasis

ProteoStat® Aggresome Detection Kit
ProteoStat™ Protein Aggregation Assay
ProteoStat™ Thermal Shift Stability Assay Kit

ProteoStat® Aggresome Detection Kit for flow cytometry and fluorescence microscopy

A DNAJB chaperone subfamily with HDAC-dependent activities suppresses toxic protein aggregation
Mol. Cell 2010, view full abstract in PubMed

Misfolding and aggregation are associated with cytotoxicity in several protein folding diseases. A large network of molecular chaperones ensures protein quality control. Here, we show that within the Hsp70, Hsp110, and Hsp40 (DNAJ) chaperone families, members of a subclass of the DNAJB family (particularly DNAJB6b and DNAJB8) are superior suppressors of aggregation and toxicity of disease-associated polyglutamine proteins. The antiaggregation activity is largely independent of the N-terminal Hsp70-interacting J-domain. Rather, a C-terminal serine-rich (SSF-SST) region and the C-terminal tail are essential. The SSF-SST region is involved in substrate binding, formation of polydisperse oligomeric complexes, and interaction with histone deacetylases (HDAC4, HDAC6, SIRT2). Inhibiting HDAC4 reduced DNAJB8 function. DNAJB8 is (de)acetylated at two conserved C-terminal lysines that are not involved in substrate binding, but do play a role in suppressing protein aggregation. Combined, our data provide a functional link between HDACs and DNAJs in suppressing cytotoxic protein aggregation.

ATP-independent reversal of a membrane protein aggregate by a chloroplast SRP subunit
Nat. Struct. Mol. Biol. 2010, view full abstract in PubMed

Membrane proteins impose enormous challenges to cellular protein homeostasis during their post-translational targeting, and they require chaperones to keep them soluble and translocation competent. Here we show that a novel targeting factor in the chloroplast signal recognition particle (cpSRP), cpSRP43, is a highly specific molecular chaperone that efficiently reverses the aggregation of its substrate proteins. In contrast to 'ATPases associated with various cellular activities' (AAA(+)) chaperones, cpSRP43 uses specific binding interactions with its substrate to mediate its 'disaggregase' activity. This disaggregase capability can allow targeting machineries to more effectively capture their protein substrates and emphasizes a close connection between protein folding and trafficking processes. Moreover, cpSRP43 provides the first example to our knowledge of an ATP-independent disaggregase and shows that efficient reversal of protein aggregation can be attained by specific binding interactions between a chaperone and its substrate.

Clearance of mutant proteins as a therapeutic target in neurodegenerative diseases
Arch. Neurol. 2010, view full abstract in PubMed

Accumulation and aggregation of disease-causing proteins is a hallmark of several neurodegenerative disorders such as Parkinson, Alzheimer, and Huntington diseases. One of the main goals of research in neurodegenerative disorders has been to improve clearance of these accumulated proteins. Using the example of Huntington disease, I discuss strategies to selectively activate cellular degradation machinery to improve clearance of the mutant protein and to identify therapeutic targets for the treatment of Huntington disease and related neurodegenerative disorders.

Loss of leucine-rich repeat kinase 2 causes impairment of protein degradation pathways, accumulation of alpha-synuclein, and apoptotic cell death in aged mice
Proc. Natl.Acad. Sci. U.S.A 2010, view full abstract in PubMed

Mutations in leucine-rich repeat kinase 2 (LRRK2) are the most common genetic cause of Parkinson's disease. LRRK2 is a large protein containing a small GTPase domain and a kinase domain, but its physiological role is unknown. To identify the normal function of LRRK2 in vivo, we generated two independent lines of germ-line deletion mice. The dopaminergic system of LRRK2(-/-) mice appears normal, and numbers of dopaminergic neurons and levels of striatal dopamine are unchanged. However, LRRK2(-/-) kidneys, which suffer the greatest loss of LRRK compared with other organs, develop striking accumulation and aggregation of alpha-synuclein and ubiquitinated proteins at 20 months of age. The autophagy-lysosomal pathway is also impaired in the absence of LRRK2, as indicated by accumulation of lipofuscin granules as well as altered levels of LC3-II and p62. Furthermore, loss of LRRK2 dramatically increases apoptotic cell death, inflammatory responses, and oxidative damage. Collectively, our findings show that LRRK2 plays an essential and unexpected role in the regulation of protein homeostasis during aging, and suggest that LRRK2 mutations may cause Parkinson's disease and cell death via impairment of protein degradation pathways, leading to alpha-synuclein accumulation and aggregation over time.

Small heat shock proteins and protein-misfolding diseases
Curr. Pharm. Biotechnol. 2010, view full abstract in PubMed

Small heat shock proteins (sHsps) are molecular chaperones ubiquitously distributed in numerous species, from bacteria to humans. A conserved C-terminal "alpha-crystallin" domain organized in a beta-sheet sandwich and oligomeric structure are common features of sHsps. sHsps protect cells against many kinds of stresses including heat shock, oxidative and osmotic stress. sHsps recognize unfolded proteins, prevent their irreversible aggregation and facilitate refolding of bound substrates in cooperation with ATP-dependent molecular chaperones (Hsp70/Hsp40). Mammalian sHsps (HSPBs) are multifunctional proteins involved in many cellular processes including those which are not directly related to protein folding and aggregation. HSPBs participate in cell development and cancerogenesis, regulate apoptosis and control cytoskeletal architecture. Recent data revealed that HSPBs also play an important role in membrane stabilization. Mutation in HSPB genes have been identified, which are responsible for the development of cataract, desmin related myopathy and neuropathies. HSPBs are often found as components of protein aggregates associated with protein-misfolding disorders, such as Parkinson's, Alzheimer's, Alexander's and prion diseases. It is supposed that the presence of HSPBs in intra- or extracellular protein deposits is a consequence of the chaperone activity of HSPBs, however more studies are needed to reveal the exact function of HSPBs during the formation (or removal) of disease-related aggregates.