Poster: Cytoskeleton structure & dynamics

Abs # 685: Profilin is a key regulator of the phosphoinositide pathway in plant

Presenter:	Sanchez, Federico , federico@ibt.unam.mx
Authors	Sanchez, Federico  (A)   Aparicio, Rosaura  (A)   Guillén, Gabriel  (A)   Estrada, Georgina  (A)   Juan, Olivares E (A)   Díaz, Diana  (A)
Affiliations:	(A): Instituto de Biotecnología, Departamento de Biología Molecular de Plantas. UNAM.
Web Site:	http://www.ibt.unam.mx

Robust actin filaments rearrangements are rapidly induced in plants responding to pathogens and symbionts (Staiger C.J. 2000; Takemoto et al, 2003). Profilin binds actin, proteins with proline- rich domains and phosphatidylinositol 4, 5-diphosphate (PIP₂). In Phaseolus vulgaris (bean) root nodules profilin is highly phosphorylated on tyrosine residues generating multiple isoforms (Guillén et al, 1999). Phosphoinositide-3 kinase (PI3K) is a key enzyme producing second messengers that signal in multiple cellular pathways. In plant cells, only the PI3K-III type (yeast Vps34-like) has been found. PI3K major functions include, endocytosis and vesicle trafficking events (Jung et al, 2002). We will present biochemical and immunological evidence describing epitopes involved in the direct interaction between PI3K and profilin of bean and other plants. PI3K activity is increased when profilin is bound. In bean, this interaction is inhibited by phosphorylation and promoted by dephosphosrylation on tyrosine residues in profilin epitopes. To our knowledge, this is the first evidence that shows direct interaction and activation of PI3K by profilin, therefore extending the link between actin cytoskeleton with the phosphoinositide signal transduction pathways. Altogether, these results highlight the key role that profilin has in cell signaling pathways, in addition to modulating actin cytoskeleton dynamics. This work was supported by grant from CONACYT No. 33350-N of México and DGAPA IN232002-2.