Depletion of mboa-7, an Enzyme That Incorporates Polyunsaturated Fatty Acids Into Phosphatidylinositol (PI), Impairs PI 3-phosphate Signaling in Caenorhabditis Elegans

Genes Cells. 2012 Sep;17(9):748-57. doi: 10.1111/j.1365-2443.2012.01624.x. Epub 2012 Aug 1.

Abstract

Phosphatidylinositol (PI) is a constituent of biomembranes and a precursor of all phosphoinositides (PIPs). A prominent characteristic of PI is that its sn-2 position is highly enriched in polyunsaturated fatty acids (PUFAs), such as arachidonic acid or eicosapentaenoic acid. However, the biological significance of PUFA-containing PI remains unknown. We previously identified Caenorhabditis elegans (C. elegans) mboa-7 as an acyltransferase that incorporates PUFAs into the sn-2 position of PI. In this study, we performed an RNAi enhancer screen against PI kinases and phosphatases using mboa-7 mutants that have a reduced PUFA content in PI. Among the genes tested, knockdown of vps-34, a catalytic subunit of class III PI 3-kinase that produces PI 3-phosphate (PI3P) from PI, caused severe growth defects in mboa-7 mutants. In both vps-34 RNAi-treated wild-type worms and mboa-7 mutants, the size of PI3P-positive early endosomes was significantly decreased. We also performed an RNAi enhancer screen against PI3P-related genes and found that, like knockdown of vps-34, knockdown of autophagy-related genes caused severe growth defects in mboa-7 mutants. Finally, we showed that autophagic clearance of protein aggregates is impaired in mboa-7 mutants. Taken together, these results suggest that the PUFA chain in PI has a role in some PI3P signaling.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acyltransferases / genetics
  • Acyltransferases / metabolism
  • Alleles
  • Animals
  • Animals, Genetically Modified / genetics
  • Animals, Genetically Modified / growth & development
  • Animals, Genetically Modified / metabolism
  • Autophagy
  • Caenorhabditis elegans / enzymology*
  • Caenorhabditis elegans / genetics
  • Caenorhabditis elegans / growth & development
  • Caenorhabditis elegans Proteins / genetics
  • Caenorhabditis elegans Proteins / metabolism*
  • Cloning, Molecular
  • Endosomes / genetics
  • Endosomes / metabolism
  • Fatty Acids, Unsaturated / genetics
  • Fatty Acids, Unsaturated / metabolism*
  • Gene Deletion
  • Gene Knockdown Techniques
  • Genetic Vectors / genetics
  • Genetic Vectors / metabolism
  • Phosphatidylinositol 3-Kinases / genetics
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphatidylinositol Phosphates / genetics
  • Phosphatidylinositol Phosphates / metabolism*
  • Phosphatidylinositols / metabolism*
  • Promoter Regions, Genetic
  • RNA Interference
  • Signal Transduction*
  • X Chromosome / genetics
  • X Chromosome / metabolism

Substances

  • Caenorhabditis elegans Proteins
  • Fatty Acids, Unsaturated
  • Phosphatidylinositol Phosphates
  • Phosphatidylinositols
  • phosphatidylinositol 3-phosphate
  • Acyltransferases
  • Phosphatidylinositol 3-Kinases