Open AccessGlycolipid Intermembrane Transfer Is Accelerated by HET-C2, a Filamentous Fungus Gene Product Involved in the Cell−Cell Incompatibility Response
Author(s) -
Peter Mattjus,
Béatrice Turcq,
Helen M. Pike,
Julian G. Molotkovsky,
Rhoderick E. Brown
Publication year - 2002
Publication title -
biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.43
H-Index - 253
eISSN - 1520-4995
pISSN - 0006-2960
DOI - 10.1021/bi026896x
Subject(s) - podospora anserina , heterokaryon , glycolipid , plant lipid transfer proteins , biology , gene , gene product , fusion protein , biochemistry , microbiology and biotechnology , gene expression , recombinant dna , mutant
Among filamentous fungi capable of mycelial growth, het genes play crucial roles by regulating heterokaryon formation between different individuals. When fusion occurs between fungal mycelia that differ genetically at their het loci, the resulting heterokaryotic cells are quickly destroyed. It is unclear how het gene products of Podospora anserina trigger heterokaryon incompatibility. One unexplored possibility is that glycosphingolipids play a role because the het-c2 gene encodes a protein that displays 32% sequence identity and an additional 30% similarity to the mammalian glycolipid transfer protein. Here, P. anserina protoplasts containing wild-type het-c2 genes were shown to have greater glycosphingolipid transfer activity than protoplasts with disrupted het-c2 genes, a condition previously linked to altered cell compatibility following hyphal fusion. The observed glycolipid transfer activity could not be accounted for by nonspecific lipid transfer protein activity. Direct assessment showed that purified, recombinant HET-C2 accelerates the intermembrane transfer of glycolipid in vitro, but that the HET-C2 activity is mitigated much less by negatively charged membranes than the mammalian glycolipid transfer protein. The findings are discussed within the context of HET-C2 being a member of an emerging family of ancestral sphingolipid transfer proteins that play important roles in cell proliferation and accelerated death.