Inositol (1,4,5)-trisphosphate receptor links to filamentous actin are important for generating local Ca2+ signals in pancreatic acinar cells.
We explored a potential structural and functional link between filamentous actin (F-actin) and inositol (1,4,5)-trisphosphate receptors (IP(3)Rs) in mouse pancreatic acinar cells. Using immunocytochemistry, F-actin and type 2 and 3 IP(3)Rs (IP(3)R2 and IP(3)R3) were identified in a cellular compartment immediately beneath the apical plasma membrane. In an effort to demonstrate that IP(3)R distribution is dependent on an intact F-actin network in the apical subplasmalemmal region, cells were treated with the actin-depolymerising agent latrunculin B. Immunocytochemistry indicated that latrunculin B treatment reduced F-actin in the basolateral subplasmalemmal compartment, and reduced and fractured F-actin in the apical subplasmalemmal compartment. This latrunculin-B-induced loss of F-actin in the apical region coincided with a reduction in IP(3)R2 and IP(3)R3, with the remaining IP(3)Rs localized with the remaining F-actin. Experiments using western blot analysis showed that IP(3)R3s are resistant to extraction by detergents, which indicates a potential interaction with the cytoskeleton. Latrunculin B treatment in whole-cell patch-clamped cells inhibited Ca(2+)-dependent Cl(-) current spikes evoked by inositol (2,4,5)-trisphosphate; this is due to an inhibition of the underlying local Ca(2+) signal. Based on these findings, we suggest that IP(3)Rs form links with F-actin in the apical domain and that these links are essential for the generation of local Ca(2+) spikes.
Turvey
Matthew R
MR
Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 IPD, UK.
Fogarty
Kevin E
KE
Thorn
Peter
P
D008841:Actin Cytoskeleton / Q000737:chemistry* / Q000378:metabolism; D000199:Actins / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000737:chemistry / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism / Q000502:physiology*; D020013:Calcium Signaling; D002462:Cell Membrane / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D003902:Detergents / Q000494:pharmacology; D004594:Electrophysiology; D018260:Gelsolin / Q000737:chemistry; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007150:Immunohistochemistry; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007295:Inositol Phosphates / Q000378:metabolism; D008297:Male; D051379:Mice; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D010179:Pancreas / Q000166:cytology*; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism / Q000502:physiology*; D013844:Thiazoles / Q000737:chemistry / Q000494:pharmacology; D053778:Thiazolidines
D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D015220:Calcium Channels; D003902:Detergents; D018260:Gelsolin; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007295:Inositol Phosphates; D018160:Receptors, Cytoplasmic and Nuclear; D013844:Thiazoles; D053778:Thiazolidines; D049452:Green Fluorescent Proteins; C062616:inositol 2,4,5-trisphosphate; C037068:latrunculin B; D002118:Calcium