title: Myosin VI and its binding partner optineurin are involved in secretory vesicle fusion at the plasma membrane.
abstract: During constitutive secretion, proteins synthesized at the endoplasmic reticulum (ER) are transported to the Golgi complex for processing and then to the plasma membrane for incorporation or extracellular release. This study uses a unique live-cell constitutive secretion assay to establish roles for the molecular motor myosin VI and its binding partner optineurin in discrete stages of secretion. Small interfering RNA-based knockdown of myosin VI causes an ER-to-Golgi transport delay, suggesting an unexpected function for myosin VI in the early secretory pathway. Depletion of myosin VI or optineurin does not affect the number of vesicles leaving the trans-Golgi network (TGN), indicating that these proteins do not function in TGN vesicle formation. However, myosin VI and optineurin colocalize with secretory vesicles at the plasma membrane. Furthermore, live-cell total internal reflection fluorescence microscopy demonstrates that myosin VI or optineurin depletion reduces the total number of vesicle fusion events at the plasma membrane and increases both the proportion of incomplete fusion events and the number of docked vesicles in this region. These results suggest a novel role for myosin VI and optineurin in regulation of fusion pores formed between secretory vesicles and the plasma membrane during the final stages of secretion.
authors.affiliation: Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB20XY, United Kingdom.
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Bond
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Peden
authors.forename: John
authors.initials: J
authors.lastname: Kendrick-Jones
authors.forename: James R
authors.initials: JR
authors.lastname: Sellers
authors.forename: Folma
authors.initials: F
authors.lastname: Buss
mesh_terms: D001692:Biological Transport; D018797:Cell Cycle Proteins; D002462:Cell Membrane / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005089:Exocytosis; D005455:Fluorescent Antibody Technique; D055785:Gene Knockdown Techniques; D006056:Golgi Apparatus / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D008561:Membrane Fusion; D008565:Membrane Proteins / Q000378:metabolism; D026901:Membrane Transport Proteins; D008856:Microscopy, Fluorescence; D018995:Myosin Heavy Chains / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering; D055571:Secretory Pathway; D022142:Secretory Vesicles / Q000378:metabolism*; D035582:Transcription Factor TFIIIA / Q000235:genetics / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D009687:Nuclear Proteins; C409460:OPTN protein, human; D034741:RNA, Small Interfering; D035582:Transcription Factor TFIIIA; C089785:myosin VI; D018995:Myosin Heavy Chains