Defining the physiological role of SRP in protein-targeting efficiency and specificity

Area of Science:

• Cell Biology
• Molecular Biology
• Protein Trafficking

Background:

• The signal recognition particle (SRP) mediates protein translocation into the endoplasmic reticulum (ER).
• Its complete in vivo function and targeting mechanisms remain incompletely understood.
• Existing models primarily focus on signal sequence recognition.

Purpose of the Study:

• To elucidate the in vivo role of SRP in protein targeting.
• To investigate SRP's function beyond signal sequence recognition.
• To understand the consequences of SRP loss on protein localization and cellular function.

Main Methods:

• Utilized rapid auxin-induced SRP degradation in yeast.
• Employed proximity-specific ribosome profiling for in vivo analysis.
• Combined genetic manipulation with high-throughput molecular profiling.

Main Results:

• SRP is essential for targeting transmembrane domains, irrespective of their location.
• Proteins with cleavable signal peptides can be targeted efficiently without SRP.
• Loss of SRP leads to mistargeting of ER-bound transcripts to mitochondria, causing defects.

Conclusions:

• SRP plays a broader role in protein targeting than previously thought, particularly for transmembrane domains.
• SRP is critical for maintaining the specificity of protein delivery to the ER.
• Disruption of SRP function has significant cellular consequences, including mitochondrial dysfunction.