protein import into peroxisome matrix, receptor recycling

Definition

Target type: biologicalprocess

The process in which peroxisome targeting sequence receptors dissociates from cargo proteins and are returned to the cytosol. [PMID:11687502]

Protein import into the peroxisome matrix is a complex and highly regulated process that relies on a specific set of receptors and translocators. Here's a breakdown of the process, including receptor recycling:

**1. Recognition and Binding:**
- Peroxisomal targeting signals (PTS) on newly synthesized proteins destined for the peroxisome matrix are recognized by PTS receptors.
- There are two main PTS receptors: Pex5 for PTS1 and Pex7 for PTS2.
- Pex5 and Pex7 bind their respective PTSs on cargo proteins.

**2. Translocation through the Peroxisomal Membrane:**
- The receptor-cargo complex interacts with the peroxisomal membrane protein Pex14.
- This interaction triggers the translocation of the cargo protein across the peroxisomal membrane via the peroxisomal translocon (Pex13, Pex17, and Pex21).

**3. Receptor Release and Recycling:**
- After cargo protein translocation, the PTS receptor (Pex5 or Pex7) is released from the translocon.
- Receptor recycling is crucial to ensure continued import of peroxisomal proteins.
- Pex5 is the primary receptor for PTS1, and its recycling pathway involves the following steps:
- Pex5 is monoubiquitinated by the E3 ligase complex containing Pex2, Pex10, and Pex12.
- Monoubiquitination targets Pex5 for interaction with the AAA ATPase complex (Pex1 and Pex6).
- The AAA ATPase complex extracts Pex5 from the peroxisomal membrane.
- Deubiquitination of Pex5 by the deubiquitinase Pex4 allows it to return to the cytosol for another round of import.
- Recycling of Pex7 (PTS2 receptor) is less well characterized, but likely involves similar mechanisms.

**4. Cargo Protein Folding and Maturation:**
- Once inside the peroxisome matrix, cargo proteins fold into their functional conformations and undergo post-translational modifications.

**5. Receptor Deficiency and Peroxisome Biogenesis Disorders:**
- Mutations in the genes encoding peroxisomal import components can disrupt the import process and lead to peroxisome biogenesis disorders.
- These disorders result in the accumulation of unprocessed proteins and deficiencies in peroxisomal function, leading to various metabolic defects.

**Overall, receptor recycling is essential for maintaining efficient peroxisomal protein import. It ensures that receptors are readily available to bind new cargo proteins and facilitate their delivery to the peroxisome matrix. Proper functioning of this process is crucial for normal peroxisome function and overall cellular health.**'
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Proteins (1)

Compounds (1)