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The yeast magmas ortholog pam16 has an essential function in fermentative growth that involves sphingolipid

Mary K Short1, Joshua P Hallett, Krisztina Tar

  • 1Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, New York, United States of America.

Plos One
|July 19, 2012
PubMed

Insights

Impaired Pam16/Magmas function affects mitochondrial protein import and causes growth defects. Compensatory pathways involving sphingolipid metabolism were identified, suggesting lipid metabolism changes mediate these effects.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Genetics

Background:

  • Magmas is a growth factor-responsive gene encoding an essential mitochondrial protein in mammals.
  • Pam16 is the Saccharomyces cerevisiae ortholog of Magmas and a component of the presequence translocase-associated motor.
  • Understanding Pam16 function is crucial for comprehending mitochondrial protein import and cellular homeostasis.

Purpose of the Study:

  • To investigate the genetic interactions and compensatory pathways associated with impaired Pam16 function using a temperature-sensitive yeast strain.
  • To identify genes that, when deleted, cause synthetic lethality or sickness with a pam16-I61N mutation.
  • To discover genes that suppress the growth defects of the pam16-I61N mutant, revealing compensatory mechanisms.

Main Methods:

  • Utilized a temperature-sensitive allele (pam16-I61N) of the yeast gene PAM16.
  • Performed a synthetic genetic array screen with a non-essential gene-deletion library to identify synthetic lethal/sick interactions.
  • Screened the same library for suppressors of the pam16-I61N growth defect.
  • Analyzed cellular phenotypes including growth, morphology, peroxisome induction, and sphingolipid levels.

Main Results:

  • The pam16-I61N mutation exhibited synthetic lethality/sickness with genes involved in lipid metabolism, peroxisome synthesis, histone deacetylation, and mitochondrial protein import.
  • Five suppressor genes (SUR4, ISC1, IPT1, SKN1, FEN1) involved in sphingolipid metabolism were identified.
  • Pam16-I61N cells showed growth inhibition, G1 cell cycle arrest, altered mitochondrial morphology, reduced peroxisome induction, and changes in sphingolipid levels (e.g., C18 alpha-hydroxy-phytoceramide).
  • Deletion of suppressor genes, particularly SUR4, reversed growth defects, morphological changes, and normalized C18 alpha-hydroxy-phytoceramide levels.

Conclusions:

  • Impaired Pam16/Magmas function leads to pleiotropic cellular effects, including mitochondrial dysfunction and altered lipid metabolism.
  • Sphingolipid metabolism plays a critical role in compensating for defects in Pam16/Magmas function.
  • Changes in lipid metabolism, particularly sphingolipids, are key mediators of the observed phenotypes associated with impaired Pam16/Magmas.
  • These findings highlight the intricate link between mitochondrial protein import and cellular lipid homeostasis.

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