title: Single-molecule analysis of chemoattractant-stimulated membrane recruitment of a PH-domain-containing protein.
abstract: Molecular mechanisms of chemotactic response are highly conserved among many eukaryotic cells including human leukocytes and Dictyostelium discoideum cells. The cells can sense the differences in chemoattractant concentration across the cell body and respond by extending pseudopods from the cell side facing to a higher concentration. Pseudopod formation is regulated by binding of pleckstrin homology (PH)-domain-containing proteins to phosphatidylinositol 3,4,5-trisphosphates [PtdIns(3,4,5)P3] localized at the leading edge of chemotaxing cells. However, molecular mechanisms underlying dynamic features of a pseudopod have not been fully explained by the known properties of PH-domain-containing proteins. To investigate the mechanisms, we visualized single molecules of green fluorescent protein tagged to Crac (Crac-GFP), a PH-domain-containing protein in D. discoideum cells. Whereas populations of Crac molecules exhibited a stable steady-state localization at pseudopods, individual molecules bound transiently to PtdIns(3,4,5)P3 for approximately 120 milliseconds, indicating dynamic properties of the PH-domain-containing protein. Receptor stimulation did not alter the binding stability but regulated the number of bound PH-domain molecules by metabolism of PtdIns(3,4,5)P3. These results demonstrate that the steady-state localization of PH-domain-containing proteins at the leading edge of chemotaxing cells is dynamically maintained by rapid recycling of individual PH-domain-containing proteins. The short interaction between PH domains and PtdIns(3,4,5)P3 contributes to accurate and sensitive chemotactic movements through the dynamic redistributions. These dynamic properties might be a common feature of signaling components involved in chemotaxis.
authors.affiliation: Laboratories for Nanobiology, Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan.
authors.forename: Satomi
authors.initials: S
authors.lastname: Matsuoka
authors.forename: Miho
authors.initials: M
authors.lastname: Iijima
authors.forename: Tomonobu M
authors.initials: TM
authors.lastname: Watanabe
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Kuwayama
authors.forename: Toshio
authors.initials: T
authors.lastname: Yanagida
authors.forename: Peter N
authors.initials: PN
authors.lastname: Devreotes
authors.forename: Masahiro
authors.initials: M
authors.lastname: Ueda
mesh_terms: D000818:Animals; D001665:Binding Sites; D002633:Chemotaxis / Q000187:drug effects; D000242:Cyclic AMP / Q000494:pharmacology; D004023:Dictyostelium / Q000378:metabolism*; D005453:Fluorescence; D006801:Humans; D051059:PTEN Phosphohydrolase / Q000378:metabolism; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D011485:Protein Binding; D015800:Protozoan Proteins / Q000378:metabolism*
chemical_list: D018129:Phosphatidylinositol Phosphates; D015800:Protozoan Proteins; C089420:dagA protein, Dictyostelium; C060974:phosphatidylinositol 3,4,5-triphosphate; D000242:Cyclic AMP; D051059:PTEN Phosphohydrolase