title: Requirement of cortical actin organization for bombesin, endothelin, and EGF receptor internalization.
abstract: The role of actin organization in occupancy-induced receptor internalization remains poorly defined. Here we report that treatment of mouse Swiss 3T3 cells with latrunculin A, a potent inhibitor of actin polymerization (including cortical actin), inhibited the internalization of the endogenous bombesin/gastrin-releasing peptide (GRP) receptor, as judged by uptake of (125)I-labeled GRP or fluorescent Cy3-labeled bombesin. In contrast, cells pretreated with cytochalasin D showed minimal inhibition of bombesin/GRP receptor internalization. Similarly, pretreatment of Swiss 3T3 cells with the potent Rho-kinase inhibitor HA-1077, at concentrations (10-20 microM) that abrogated bombesin-mediated stress fiber formation, did not significantly alter receptor-mediated internalization of (125)I-GRP. These results indicate that bombesin/GRP receptor internalization depends on latrunculin A-sensitive cortical actin rather than on rapidly turning over actin stress fibers that are disrupted by either cytochalasin D or HA-1077. The rates and total levels of internalization of the endogenously expressed endothelin A receptor and epidermal growth factor receptor were also markedly reduced by latrunculin A in Swiss 3T3 cells. The potency of latrunculin A for inhibiting G protein-coupled receptor endocytosis was comparable to that for reducing internalization of the epidermal growth factor tyrosine kinase receptor. We conclude that cortical actin structures, disrupted by latrunculin A, are necessary for occupancy-induced receptor internalization in animal cells.
authors.affiliation: Department of Medicine, School of Medicine, Center for Ulcer Research and Education Digestive Diseases Research Center and Molecular Biology Institute, University of California, Los Angeles, California 90095, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Lunn
authors.forename: H
authors.initials: H
authors.lastname: Wong
authors.forename: E
authors.initials: E
authors.lastname: Rozengurt
authors.forename: J H
authors.initials: JH
authors.lastname: Walsh
mesh_terms: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000031:analogs & derivatives* / Q000494:pharmacology; D016475:3T3 Cells; D000199:Actins / Q000378:metabolism*; D000818:Animals; D001839:Bombesin / Q000493:pharmacokinetics; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D015638:Cytochalasin D / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000493:pharmacokinetics; D066246:ErbB Receptors / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism; D019886:Gastrin-Releasing Peptide / Q000493:pharmacokinetics; D007457:Iodine Radioisotopes; D007700:Kinetics; D051379:Mice; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D010766:Phosphorylation; D018004:Receptors, Bombesin / Q000378:metabolism*; D017466:Receptors, Endothelin / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines
chemical_list: D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D004791:Enzyme Inhibitors; D007457:Iodine Radioisotopes; D019384:Nucleic Acid Synthesis Inhibitors; D018004:Receptors, Bombesin; D017466:Receptors, Endothelin; D013844:Thiazoles; D053778:Thiazolidines; D015638:Cytochalasin D; D004815:Epidermal Growth Factor; D019886:Gastrin-Releasing Peptide; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D066246:ErbB Receptors; D019204:GTP-Binding Proteins; D001839:Bombesin; C049347:fasudil; C037067:latrunculin A