In-Gel Nonspecific Proteolysis for Elucidating Glycoproteins: A Method for Targeted Protein-Specific Glycosylation Analysis in Complex Protein Mixtures

AbstractATP-independent chaperones are usually considered to be holdases that rapidly bind to non-native states of substrate proteins and prevent their aggregation. These chaperones are thought to release their substrate proteins prior to their folding. Spy is an ATP-independent chaperone that acts as an aggregation inhibiting holdase but does so by allowing its substrate proteins to fold while they remain continuously chaperone bound, thus acting as a foldase as well. The attributes that allow such dual chaperoning behavior are unclear. Here, we used the topologically complex protein apoflavodoxin to show that the outcome of Spy’s action is substrate specific and depends on its relative affinity for different folding states. Tighter binding of Spy to partially unfolded states of apoflavodoxin limits the possibility of folding while bound, converting Spy to a holdase chaperone. Our results highlight the central role of the substrate in determining the mechanism of chaperone action.

Download Full-text

Breakdown of Filamentous Myofibrils by the UPS–Step by Step

Biomolecules ◽

10.3390/biom11010110 ◽

2021 ◽

Vol 11 (1) ◽

pp. 110

Author(s):

Dina Aweida ◽

Shenhav Cohen

Keyword(s):

Protein Quality ◽

Protein Structures ◽

Ubiquitin Proteasome System ◽

Surface Proteins ◽

Catalytic Core ◽

Complex Protein ◽

Ubiquitin Proteasome ◽

Aaa Atpases

Protein degradation maintains cellular integrity by regulating virtually all biological processes, whereas impaired proteolysis perturbs protein quality control, and often leads to human disease. Two major proteolytic systems are responsible for protein breakdown in all cells: autophagy, which facilitates the loss of organelles, protein aggregates, and cell surface proteins; and the ubiquitin-proteasome system (UPS), which promotes degradation of mainly soluble proteins. Recent findings indicate that more complex protein structures, such as filamentous assemblies, which are not accessible to the catalytic core of the proteasome in vitro, can be efficiently degraded by this proteolytic machinery in systemic catabolic states in vivo. Mechanisms that loosen the filamentous structure seem to be activated first, hence increasing the accessibility of protein constituents to the UPS. In this review, we will discuss the mechanisms underlying the disassembly and loss of the intricate insoluble filamentous myofibrils, which are responsible for muscle contraction, and whose degradation by the UPS causes weakness and disability in aging and disease. Several lines of evidence indicate that myofibril breakdown occurs in a strictly ordered and controlled manner, and the function of AAA-ATPases is crucial for their disassembly and loss.

Download Full-text

Disrupting the LINC complex by AAV mediated gene transduction prevents progression of Lamin induced cardiomyopathy

Nature Communications ◽

10.1038/s41467-021-24849-4 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Ruth Jinfen Chai ◽

Hendrikje Werner ◽

Peter Yiqing Li ◽

Yin Loon Lee ◽

Khaing Thet Nyein ◽

...

Keyword(s):

Cardiac Failure ◽

Viral Vector ◽

Nuclear Periphery ◽

Dominant Negative ◽

Gene Transduction ◽

Linc Complex ◽

Specific Expression ◽

Common Cause ◽

Complex Protein ◽

One Year

AbstractMutations in the LaminA gene are a common cause of monogenic dilated cardiomyopathy. Here we show that mice with a cardiomyocyte-specific Lmna deletion develop cardiac failure and die within 3–4 weeks after inducing the mutation. When the same Lmna mutations are induced in mice genetically deficient in the LINC complex protein SUN1, life is extended to more than one year. Disruption of SUN1’s function is also accomplished by transducing and expressing a dominant-negative SUN1 miniprotein in Lmna deficient cardiomyocytes, using the cardiotrophic Adeno Associated Viral Vector 9. The SUN1 miniprotein disrupts binding between the endogenous LINC complex SUN and KASH domains, displacing the cardiomyocyte KASH complexes from the nuclear periphery, resulting in at least a fivefold extension in lifespan. Cardiomyocyte-specific expression of the SUN1 miniprotein prevents cardiomyopathy progression, potentially avoiding the necessity of developing a specific therapeutic tailored to treating each different LMNA cardiomyopathy-inducing mutation of which there are more than 450.

Download Full-text