title: Cytoskeletal regulation of ion channel distribution in the tip-growing organism Saprolegnia ferax.
abstract: Growing hyphal tips of the oomycete Saprolegnia ferax possess a tip-high gradient of stretch-activated ion channels permeable to calcium. These mechanosensitive channels appear to play a direct role in the polarized tip growth process. Treatment of S. ferax hyphae with cytochalasin E leads to the disruption of plasmalemma-associated, peripheral cytoplasmic actin populations and altered morphology of apical protoplasts, and eliminates the tip-high gradient of stretch-activated channels. Cytochalasin E did not alter the normal aggregation of stretch-activated channels. The density of spontaneous K+ channels was decreased in all regions of the hyphae after treatment with cytochalasin E. These results suggest that the peripheral F-actin network in the growing tip of S. ferax hyphae establishes or maintains the tip-high gradient of SA channels, either by the delivery of channel-bearing vesicles to the apex or by the interactions between the channels and the peripheral actin network.
authors.affiliation: York University Biology Department, Ontario, Canada.
authors.forename: N N
authors.initials: NN
authors.lastname: Levina
authors.forename: R R
authors.initials: RR
authors.lastname: Lew
authors.forename: I B
authors.initials: IB
authors.lastname: Heath
mesh_terms: D003572:Cytochalasins / Q000494:pharmacology; D003599:Cytoskeleton / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure*; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D004594:Electrophysiology / Q000379:methods; D005658:Fungi / Q000187:drug effects / Q000254:growth & development / Q000648:ultrastructure*; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology; D011523:Protoplasts / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure
chemical_list: D003572:Cytochalasins; D007473:Ion Channels; D015221:Potassium Channels; C007215:cytochalasin E; D004121:Dimethyl Sulfoxide