HspB8 mutation causing hereditary distal motor neuropathy impairs lysosomal delivery of autophagosomes.

HspB8, a small heat-shock protein implicated in autophagy, is mutated in patients with distal hereditary motor neuropathy type II (dHMNII). Autophagy is essential for maintaining protein homeostasis in the central nervous system, but its role has not been investigated in peripheral motor neurons. We used a novel, multispectral-imaging flow cytometry assay to measure autophagy in cells.

Transcriptional and cellular responses to defective mitochondrial proteolysis in fission yeast.

Lon and m-AAA are the principal, regulated proteases required for protein maturation and turnover in the mitochondrial matrix of diverse species. To understand their roles in fission yeast (Schizosaccharomyces pombe) mitochondria, we generated deletion strains lacking Lon and m-AAA, individually (Δlon1 and Δm-AAA) or together, Δlon1Δm-AAA (Δ/Δ). All three strains were viable but incapable of respiratory growth on a non-fermentable carbon source due to mitochondrial dysfunction.

Real-time observation of trigger factor function on translating ribosomes.

The contribution of co-translational chaperone functions to protein folding is poorly understood. Ribosome-associated trigger factor (TF) is the first molecular chaperone encountered by nascent polypeptides in bacteria. Here we show, using fluorescence spectroscopy to monitor TF function and structural rearrangements in real time, that TF interacts with ribosomes and translating polypeptides in a dynamic reaction cycle.

Pathways of chaperone-mediated protein folding in the cytosol.

Cells are faced with the task of folding thousands of different polypeptides into a wide range of conformations. For many proteins, the folding process requires the action of molecular chaperones. In the cytosol of prokaryotic and eukaryotic cells, molecular chaperones of different structural classes form a network of pathways that can handle substrate polypeptides from the point of initial synthesis on ribosomes to the final stages of folding.

Function of trigger factor and DnaK in multidomain protein folding: increase in yield at the expense of folding speed.

Trigger factor and DnaK protect nascent protein chains from misfolding and aggregation in the E. coli cytosol, but how these chaperones affect the mechanism of de novo protein folding is not yet understood. Upon expression under chaperone-depleted conditions, multidomain proteins such as bacterial beta-galactosidase (beta-gal) and eukaryotic luciferase fold by a rapid but inefficient default pathway, tightly coupled to translation.