title: Myosin IIB isoform plays an essential role in the formation of two distinct types of macropinosomes.
abstract: The function and mechanism of macropinocytosis in cells outside of the immune system remain poorly understood. We used a neuroblastoma cell line, Neuro-2a, to study macropinocytosis in neuronal cells. We found that phorbol 12-myristate 13-acetate (PMA) and insulin-like growth factor 1 (IGF-1) induced two distinct types of macropinocytosis in the Neuro-2a cells. IGF-1-induced macropinocytosis occurs mostly around the cell bodies and requires phosphoinositide 3-kinase (PI3K), while PMA-induced macropinocytosis occurs predominantly in the neurites and is independent of PI3K activity. Both types of macropinocytosis were inhibited by a specific inhibitor of nonmuscle myosin II, blebbistatin. siRNA knockdown of nonmuscle myosin II isoforms, -IIA and -IIB, resulted in opposite effects on macropinocytosis induced by PMA or IGF. Myosin IIA knockdown significantly increased, whereas myosin IIB knockdown significantly decreased, macropinocytosis with correlating changes in membrane ruffle formation.
authors.affiliation: Department of Medicine and Cell Biology, Program in Neuroscience, University of Massachusetts Medical School, Worcester, Massachusetts.
authors.forename: Jun
authors.initials: J
authors.lastname: Jiang
authors.forename: Adrianne L
authors.initials: AL
authors.lastname: Kolpak
authors.forename: Zheng-Zheng
authors.initials: ZZ
authors.lastname: Bao
mesh_terms: D000818:Animals; D015153:Blotting, Western; D045744:Cell Line, Tumor; D005455:Fluorescent Antibody Technique; D006576:Heterocyclic Compounds, 4 or More Rings / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D051379:Mice; D024501:Nonmuscle Myosin Type IIB / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D010873:Pinocytosis / Q000187:drug effects; D011109:Polymethacrylic Acids / Q000494:pharmacology; D020033:Protein Isoforms / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism
chemical_list: D006576:Heterocyclic Compounds, 4 or More Rings; D011109:Polymethacrylic Acids; D020033:Protein Isoforms; C472645:blebbistatin; D007334:Insulin-Like Growth Factor I; D024501:Nonmuscle Myosin Type IIB