α-Internexin and Peripherin: Expression, Assembly, Functions, and Roles in Disease

Area of Science:

• Neuroscience
• Cell Biology
• Protein Biochemistry

Background:

• α-Internexin and peripherin are neuronal-specific intermediate filament (IF) proteins.
• α-Internexin is a type IV IF protein, similar to neurofilament triplet proteins (NFTPs), and is proposed as a fourth neurofilament subunit in the CNS.
• Peripherin is a type III IF protein, predominantly expressed in the PNS, and is considered a fourth neurofilament subunit in the PNS.

Purpose of the Study:

• To elucidate the roles and characteristics of α-internexin and peripherin as neuronal IF proteins.
• To investigate the potential of α-internexin and peripherin as additional neurofilament subunits.
• To explore the involvement of peripherin in neurodegenerative diseases like ALS.

Main Methods:

• In vitro self-polymerization assays.
• Analysis of protein expression in transfected cells.
• Examination of protein presence during development and in specific neuronal populations (cerebellum, sciatic nerve).
• Investigation of peripherin isoforms and their potential functional significance.
• Analysis of peripherin in patient samples with amyotrophic lateral sclerosis (ALS).

Main Results:

• α-Internexin self-polymerizes and is present in the absence of NFTPs during development and in cerebellar granule cells.
• Peripherin self-assembles, is abundant in the PNS, and exhibits multiple isoforms whose functions are unclear.
• Peripherin is a major component of inclusions in ALS patients, with upregulated expression.

Conclusions:

• α-Internexin and peripherin are crucial neuronal IF proteins with distinct CNS and PNS roles, respectively.
• Both proteins can function as additional neurofilament subunits.
• Peripherin's association with ALS highlights its potential role in neurodegeneration.