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The Proteasome02:18

The Proteasome

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Eukaryotic cells can degrade proteins through several pathways. One of the most important amongst these is the ubiquitin-proteasome pathway. It helps the cell eliminate the misfolded, damaged, or unwarranted cytoplasmic proteins in a highly specific manner.
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Mitochondrial Precursor Proteins01:39

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Mitochondrial precursors are partially unfolded or loosely folded polypeptide chains. Newly synthesized precursors are inhibited from spontaneously folding into their native conformation by the cytosolic chaperones, heat shock proteins 70 (Hsp70), and mitochondrial import stimulation factors (MSFs). Precursors bound to MSFs are guided to the TOM70-TOM37 receptors, while precursors bound to Hsp70  chaperones are targetted to TOM20-TOM22 receptor complexes.
Most of the mitochondrial...
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Translocation of Proteins into the Mitochondria01:19

Translocation of Proteins into the Mitochondria

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Mitochondrial precursors are translocated to the internal subcompartments via independent mechanisms involving distinct protein machineries called translocases.
Sorting of outer membrane proteins:
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The Unfolded Protein Response01:37

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The ER is the hub of protein synthesis in a cell. It has robust systems to quality control protein folding and also for degradation of terminally misfolded proteins. Under normal conditions, a small proportion of misfolded proteins that cannot be salvaged need to be transported to the cytoplasm by the ER-associated degradation or ERAD pathways. However, if the ERAD cannot handle the misfolded proteins, the cell activates the unfolded protein response or UPR to adjust the protein folding...
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Export of Misfolded Proteins out of the ER01:32

Export of Misfolded Proteins out of the ER

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After folding, the ER assesses the quality of secretory and membrane proteins. The correctly folded proteins are cleared by the calnexin cycle for transport to their final destination, while misfolded proteins are held back in the ER lumen. The ER chaperones attempt to unfold and refold the misfolded proteins but sometimes fail to achieve the correct native conformation. Such terminally misfolded proteins are then exported to the cytosol by ER-associated degradation or ERAD pathway for...
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The Proteasome01:13

The Proteasome

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Eukaryotic cells can degrade proteins through several pathways. One of the most important among these is the ubiquitin-proteasome pathway. It helps the cell eliminate the misfolded, damaged, or unwarranted cytoplasmic proteins in a highly specific manner.
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Imaging the Intracellular Trafficking of APP with Photoactivatable GFP
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Intramembrane proteolysis by presenilins.

H Steiner1, C Haass

  • 1Adolf Butenandt-Institute, Department of Biochemistry, Laboratory for Alzheimer's Disease Research, Ludwig-Maximilians University, 80336 Munich, Germany.

Nature Reviews. Molecular Cell Biology
|March 17, 2001
PubMed
Summary

Researchers identified presenilin as a secretase enzyme involved in producing amyloid beta-peptide (A beta). This finding advances understanding of neurodegenerative diseases like Alzheimer's and presenilin's role.

Area of Science:

  • Neurobiology
  • Molecular Biology
  • Biochemistry

Background:

  • Neurodegenerative diseases are characterized by the accumulation of insoluble amyloid molecules.
  • Amyloid beta-peptide (A beta) is a primary component of senile plaques in Alzheimer's disease.

Purpose of the Study:

  • To identify the secretase enzyme responsible for generating amyloid beta-peptide (A beta).
  • To elucidate the role of presenilin in the context of amyloid deposition.

Main Methods:

  • Investigated the enzymatic activity of secretases involved in amyloid precursor protein processing.
  • Utilized biochemical assays to characterize enzyme function and substrate interaction.

Main Results:

  • Identified presenilin as a key secretase enzyme implicated in A beta generation.

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  • Established a link between presenilin activity and the formation of amyloid plaques.

    • Conclusions:

    • The identification of presenilin as a secretase offers a new avenue for understanding Alzheimer's disease pathogenesis.
    • Further research into presenilin's structure and function is crucial for developing therapeutic strategies.