title: βIII spectrin regulates the structural integrity and the secretory protein transport of the Golgi complex.
abstract: A spectrin-based cytoskeleton is associated with endomembranes, including the Golgi complex and cytoplasmic vesicles, but its role remains poorly understood. Using new generated antibodies to specific peptide sequences of the human βIII spectrin, we here show its distribution in the Golgi complex, where it is enriched in the trans-Golgi and trans-Golgi network. The use of a drug-inducible enzymatic assay that depletes the Golgi-associated pool of PI4P as well as the expression of PH domains of Golgi proteins that specifically recognize this phosphoinositide both displaced βIII spectrin from the Golgi. However, the interference with actin dynamics using actin toxins did not affect the localization of βIII spectrin to Golgi membranes. Depletion of βIII spectrin using siRNA technology and the microinjection of anti-βIII spectrin antibodies into the cytoplasm lead to the fragmentation of the Golgi. At ultrastructural level, Golgi fragments showed swollen distal Golgi cisternae and vesicular structures. Using a variety of protein transport assays, we show that the endoplasmic reticulum-to-Golgi and post-Golgi protein transports were impaired in βIII spectrin-depleted cells. However, the internalization of the Shiga toxin subunit B to the endoplasmic reticulum was unaffected. We state that βIII spectrin constitutes a major skeletal component of distal Golgi compartments, where it is necessary to maintain its structural integrity and secretory activity, and unlike actin, PI4P appears to be highly relevant for the association of βIII spectrin the Golgi complex.
authors.affiliation: Department de Biologia Cel·lular, Immunologia i Neurociències, Facultat de Medicina, Universitat de Barcelona, 08036 Barcelona, Spain.
authors.forename: Laia
authors.initials: L
authors.lastname: Salcedo-Sicilia
authors.forename: Susana
authors.initials: S
authors.lastname: Granell
authors.forename: Marko
authors.initials: M
authors.lastname: Jovic
authors.forename: Adrià
authors.initials: A
authors.lastname: Sicart
authors.forename: Eugenia
authors.initials: E
authors.lastname: Mato
authors.forename: Ludger
authors.initials: L
authors.lastname: Johannes
authors.forename: Tamas
authors.initials: T
authors.lastname: Balla
authors.forename: Gustavo
authors.initials: G
authors.lastname: Egea
mesh_terms: D000818:Animals; D001692:Biological Transport; D019556:COS Cells; D002462:Cell Membrane / Q000378:metabolism; D002522:Chlorocebus aethiops; D003599:Cytoskeleton / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology; D006056:Golgi Apparatus / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D021381:Protein Transport; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D013049:Spectrin / Q000235:genetics* / Q000502:physiology*; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D034741:RNA, Small Interfering; C495133:SPTBN2 protein, human; D013049:Spectrin