EMBO Fellows Meeting 2012

Ylva Ivarsson
EMBO Fellows Meeting 2012
Integration of peptide and lipid interactions by PDZ domains
Abstract
PDZ domains are abundant protein modules well-known for contributing to the scaffolding function of their
host proteins by recognizing short C-terminal peptides. Some PDZ domains may also interact with
phosphoinositides (PtdInsPs), which have important biological implications as PtdInsPs are key lipids in the
regulation of various cellular processes such as intracellular signaling, cytoskeleton reorganization, vesicular
trafficking and cell polarization. The specific objectives of my project were to elucidate the prevalence of highaffinity
PDZ-PtdInsPs interactions in the human proteome, clarify structural details of such interactions, and
investigate the interplay between peptide and PtdInsPs interactions in vitro and in vivo. Toward this end, I
screened the human proteome for PDZ-PtdInsPs interactions by cell-localization studies combined with in vitro
binding experiments using synthetic lipids and recombinant proteins. A subset of PDZ domains localized to
distinct cellular compartments such as plasma membrane and peroxisomes and these domains tend to
interact with PtdInsPs in vitro. The specificities for the inositide head group were generally low, but there was
a trend of higher affinities for more phosphorylated PtdInsPs species. PtdInsPs interacting PDZ domains are
characterized by high pI values. We identified distinct properties of subgroups of phospholipid binding PDZ
domains, and confirmed the conclusions by mutagenic analysis and successful prediction of additional lipid
binding proteins. The interplay between peptide and PtdInsPs binding was probed for selected cases and it
range from competitive to cooperative depending on the combination of interactants. These findings provide
general insights on PDZ-phosphoinositide interactions, which may have important implications for the biology
of the host proteins.
Terrence Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Ontario, Canada
14-17 June 2012, Heidelberg, Germany