The actin binding protein profilin 1 localizes inside mitochondria and is critical for their function

Area of Science:

• Cell Biology
• Molecular Biology
• Neuroscience

Background:

• Profilin 1 (PFN1) is essential for actin polymerization.
• PFN1 mutations are linked to hereditary amyotrophic lateral sclerosis (ALS), causing pathologies beyond its known function.
• The full physiological roles of PFN1 remain largely undiscovered.

Purpose of the Study:

• To identify novel cellular functions of PFN1 by screening for phenotypes in PFN1 knockout cells.
• To investigate the role of PFN1 in cellular pathologies associated with its loss of function.

Main Methods:

• Screening of knockout cells to identify PFN1 loss-of-function phenotypes.
• Analysis of mitophagy, autophagosome formation, lysosomal fusion, and mitochondrial quality control pathways.
• Microscopy and metabolic assays to characterize mitochondrial morphology and function.

Main Results:

• PFN1 knockout cells exhibit significantly upregulated mitophagy.
• Despite functional autophagy and other quality control pathways, PFN1 knockout cells accumulate depolarized, dysmorphic mitochondria with altered metabolism.
• PFN1 was detected within mitochondria, and observed mitochondrial defects were independent of cytosolic actin polymerization.

Conclusions:

• PFN1 plays a previously unrecognized role in maintaining mitochondrial integrity.
• PFN1's presence within mitochondria suggests a novel function beyond actin dynamics.
• PFN1 dysregulation may contribute to ALS pathogenesis through mechanisms involving mitochondrial dysfunction.