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Protein Import into the Peroxisomes

Protein Import into the Peroxisomes

Cells contain membrane-bound organelles called peroxisomes that oxidize organic molecules by transferring hydrogen atoms to oxygen, producing hydrogen peroxide. Peroxisomes enzymatically convert the released hydrogen peroxide into water and oxygen.
Peroxisomal Protein Import:
Peroxisomes lack the genetic machinery required to code for their own proteins. Hence, most peroxisomal membrane, lumenal and transmembrane proteins are synthesized in the cytoplasm or ER and transported to the peroxisome...

Peroxisomes

Peroxisomes

Peroxisomes are specialized organelles present in fungi, plant, and animal cells. It can vary in number, size, morphology, and activity depending on the type of tissue and the nutritional state of the cell. For example, cells with active lipid metabolism, such as adipocytes, neurons, and hepatocytes, have more peroxisomes than other cells in the body. Besides their primary role in breaking down complex organic molecules, peroxisomes can also synthesize specific macromolecules and participate in...

Peroxisomes and Mitochondria

Peroxisomes and Mitochondria

Peroxisomes and mitochondria are two important oxygen-utilizing organelles in eukaryotic cells. Mitochondria carry out cellular respiration—the process that converts energy from food into ATP. Peroxisomes carry out a variety of functions, primarily breaking down different substances, such as fatty acids.
The peroxisome is a single membrane-bound cellular organelle that can perform several different functions, including lipid metabolism and chemical detoxification. The enzymes within peroxisomes...

Peroxisomes

Peroxisomes

Peroxisomes are specialized organelles present in fungi, plant, and animal cells. It can vary in number, size, morphology, and activity depending on the type of tissue and the nutritional state of the cell. For example, cells with active lipid metabolism, such as adipocytes, neurons, and hepatocytes, have more peroxisomes than other cells in the body. Besides their primary role in breaking down complex organic molecules, peroxisomes can also synthesize specific macromolecules and participate in...

The Unfolded Protein Response

The Unfolded Protein Response

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...

Regulation of the Unfolded Protein Response

Regulation of the Unfolded Protein Response

Inositol-requiring kinase one or IRE1 is the most conserved eukaryotic unfolded protein response (UPR) receptor. It is a type I transmembrane protein kinase receptor with a distinctive site-specific RNase activity. As the binding mechanics of the misfolded proteins with the N-terminal domain of IRE-1 are unclear, three binding models — direct, indirect, and allosteric -- are proposed for receptor activation. Nevertheless, it is known that once a misfolded protein associates with IRE1, it...

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Related Experiment Video

Updated: May 23, 2026

Monitoring Stub1-Mediated Pexophagy

Monitoring Stub1-Mediated Pexophagy

Published on: May 12, 2023

Protein refolding in peroxisomes is dependent upon an HSF1-regulated function.

Lonneke Heldens¹, Siebe T van Genesen, Lars L P Hanssen

¹Department of Biomolecular Chemistry, Radboud University Nijmegen, The Netherlands.

Cell Stress & Chaperones

|April 6, 2012

Summary

Heat shock disrupts protein folding, requiring chaperones for refolding. A dominant-negative HSF1 mutant impaired refolding across cellular compartments, highlighting the essential role of heat shock factor 1 (HSF1)-regulated chaperones.

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Coupled Assays for Monitoring Protein Refolding in Saccharomyces cerevisiae

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Coupled Assays for Monitoring Protein Refolding in Saccharomyces cerevisiae

Coupled Assays for Monitoring Protein Refolding in Saccharomyces cerevisiae

Published on: July 9, 2013

Area of Science:

Cellular Biology
Molecular Biology
Protein Folding

Background:

Heat shock triggers cellular stress responses, including the activation of heat shock factor 1 (HSF1).
HSF1 regulates the expression of molecular chaperones crucial for protein folding and cellular proteostasis.
Impaired chaperone function can lead to protein misfolding and cellular dysfunction.

Purpose of the Study:

To investigate the role of HSF1-regulated chaperones in the post-heat shock refolding of luciferase in different subcellular compartments.
To determine the specific chaperone requirements for refolding in the cytoplasm, nucleus, peroxisomes, and endoplasmic reticulum (ER).

Main Methods:

Utilized a dominant-negative HSF1 mutant (dnHSF1) to deplete cells of HSF1-regulated chaperones.
Assessed luciferase refolding efficiency in various cellular compartments (cytoplasm, nucleus, peroxisomes, ER) following heat shock.
Investigated the effects of overexpressing specific chaperones (HSPA1A, DNAJB1, HSPB1) on refolding in both control and dnHSF1-expressing cells.

Main Results:

dnHSF1 expression significantly blocked luciferase refolding in the cytoplasm, nucleus, and peroxisomes, with a 50% inhibition in the ER.
Cytoplasmic refolding was partially restored by HSPA1A and fully by HSPA1A and DNAJB1.
ER refolding was fully restored by HSPA1A.
Nuclear and peroxisomal refolding were not rescued by HSPA1A.
DNAJB1 and HSPB1 stimulated peroxisomal refolding in control cells but not in dnHSF1-expressing cells.
HSP90, HSPA5, HSPA6, and phosphomevalonate kinase had no effect on peroxisomal refolding.

Conclusions:

Post-heat shock protein refolding is heavily dependent on HSF1-regulated chaperones across diverse cellular locations.
Specific chaperones exhibit distinct roles in refolding depending on the subcellular compartment.
Peroxisomal refolding shows an unusual requirement for DNAJB1 or HSPB1, and an unidentified HSF1-regulated factor in dnHSF1-expressing cells.