title: Endogenous plasma membrane t-SNARE syntaxin 4 is present in rab11 positive endosomal membranes and associates with cortical actin cytoskeleton.
abstract: Membrane fusion requires the formation of a complex between a vesicle protein (v-SNARE) and the target membrane proteins (t-SNAREs). Syntaxin 4 is a t-SNARE that, according to previous overexpression studies, is predominantly localized at the plasma membrane. In the present study endogenous syntaxin 4 was found in intracellular vesicular structures in addition to regions of the plasma membrane. In these vesicular structures syntaxin 4 colocalized with rab11, a marker of recycling endosomes. Furthermore, syntaxin 4 colocalized with actin at the dynamic regions of the plasma membrane. Treatment with N-ethylmaleimide, the membrane transport inhibitor, caused an increased accumulation of syntaxin 4/rab11 positive vesicles in actin filament-like structures. Finally, purified recombinant syntaxin 4 but not syntaxin 2 or 3 cosedimented with actin filaments in vitro, suggesting direct interaction between these two proteins. Taken together, these data suggest that syntaxin 4 regulates secretion at the actin-rich areas of the plasma membrane and may be recycled through rab11 positive intracellular membranes.
authors.affiliation: Department of Biosciences, Division of Biochemistry, Viikki Biocenter, University of Helsinki, P.O. Box 56, Viikinkaari 5, 00014, Helsinki, Finland. arja.band@helsinki.fi
authors.forename: Arja M
authors.initials: AM
authors.lastname: Band
authors.forename: Heidi
authors.initials: H
authors.lastname: Ali
authors.forename: Maria K
authors.initials: MK
authors.lastname: Vartiainen
authors.forename: Saara
authors.initials: S
authors.lastname: Welti
authors.forename: Pekka
authors.initials: P
authors.lastname: Lappalainen
authors.forename: Vesa M
authors.initials: VM
authors.lastname: Olkkonen
authors.forename: Esa
authors.initials: E
authors.lastname: Kuismanen
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D011992:Endosomes / Q000378:metabolism*; D005033:Ethylmaleimide / Q000494:pharmacology; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D050765:Qa-SNARE Proteins; D020691:rab GTP-Binding Proteins / Q000378:metabolism*; D000099193:rab11 GTP-Binding Proteins
chemical_list: D000199:Actins; D005033:Ethylmaleimide; D008565:Membrane Proteins; D050765:Qa-SNARE Proteins; D020691:rab GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins