title: Myosin motors and not actin comets are mediators of the actin-based Golgi-to-endoplasmic reticulum protein transport.
abstract: We have previously reported that actin filaments are involved in protein transport from the Golgi complex to the endoplasmic reticulum. Herein, we examined whether myosin motors or actin comets mediate this transport. To address this issue we have used, on one hand, a combination of specific inhibitors such as 2,3-butanedione monoxime (BDM) and 1-[5-isoquinoline sulfonyl]-2-methyl piperazine (ML7), which inhibit myosin and the phosphorylation of myosin II by the myosin light chain kinase, respectively; and a mutant of the nonmuscle myosin II regulatory light chain, which cannot be phosphorylated (MRLC2(AA)). On the other hand, actin comet tails were induced by the overexpression of phosphatidylinositol phosphate 5-kinase. Cells treated with BDM/ML7 or those that express the MRLC2(AA) mutant revealed a significant reduction in the brefeldin A (BFA)-induced fusion of Golgi enzymes with the endoplasmic reticulum (ER). This delay was not caused by an alteration in the formation of the BFA-induced tubules from the Golgi complex. In addition, the Shiga toxin fragment B transport from the Golgi complex to the ER was also altered. This impairment in the retrograde protein transport was not due to depletion of intracellular calcium stores or to the activation of Rho kinase. Neither the reassembly of the Golgi complex after BFA removal nor VSV-G transport from ER to the Golgi was altered in cells treated with BDM/ML7 or expressing MRLC2(AA). Finally, transport carriers containing Shiga toxin did not move into the cytosol at the tips of comet tails of polymerizing actin. Collectively, the results indicate that 1) myosin motors move to transport carriers from the Golgi complex to the ER along actin filaments; 2) nonmuscle myosin II mediates in this process; and 3) actin comets are not involved in retrograde transport.
authors.affiliation: Departament de Biologia Cel.lular i Anatomia Patològica, Facultat de Medicina, Institut d'Investigacions Biomèdiques August Pi i Sunyer, Universitat de Barcelona, Spain.
authors.forename: Juan M
authors.initials: JM
authors.lastname: Durán
authors.forename: Ferran
authors.initials: F
authors.lastname: Valderrama
authors.forename: Susana
authors.initials: S
authors.lastname: Castel
authors.forename: Juana
authors.initials: J
authors.lastname: Magdalena
authors.forename: Mónica
authors.initials: M
authors.lastname: Tomás
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hosoya
authors.forename: Jaime
authors.initials: J
authors.lastname: Renau-Piqueras
authors.forename: Vivek
authors.initials: V
authors.lastname: Malhotra
authors.forename: Gustavo
authors.initials: G
authors.lastname: Egea
mesh_terms: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000494:pharmacology; D000199:Actins / Q000737:chemistry* / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D020126:Brefeldin A / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D018076:DNA, Complementary / Q000378:metabolism; D003931:Diacetyl / Q000031:analogs & derivatives* / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019084:Fluorescent Antibody Technique, Indirect; D006056:Golgi Apparatus / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins / Q000378:metabolism; D009218:Myosins / Q000737:chemistry* / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D021381:Protein Transport; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D022621:Shiga Toxin / Q000494:pharmacology; D013997:Time Factors; D014759:Viral Envelope Proteins / Q000378:metabolism; D054460:rho-Associated Kinases
chemical_list: D000199:Actins; D018076:DNA, Complementary; D004791:Enzyme Inhibitors; C028391:G protein, vesicular stomatitis virus; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D011500:Protein Synthesis Inhibitors; D011994:Recombinant Proteins; D014759:Viral Envelope Proteins; C004717:diacetylmonoxime; D020126:Brefeldin A; D022621:Shiga Toxin; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D009218:Myosins; D003931:Diacetyl; D002118:Calcium