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Regulation of late endosomal/lysosomal maturation and trafficking by cortactin affects Golgi morphology
Author(s) -
Kirkbride Kellye C.,
Hong Nan Hyung,
French Christi L.,
Clark Emily S.,
Jerome W. Gray,
Weaver Alissa M.
Publication year - 2012
Publication title -
cytoskeleton
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.95
H-Index - 86
eISSN - 1949-3592
pISSN - 1949-3584
DOI - 10.1002/cm.21051
Subject(s) - cortactin , golgi apparatus , endosome , microbiology and biotechnology , biology , endoplasmic reticulum , brefeldin a , cytoskeleton , biochemistry , cell , intracellular
Cortactin is a branched actin regulator and tumor‐overexpressed protein that promotes vesicular trafficking at a variety of cellular sites, including endosomes and the trans‐Golgi network. To better understand its role in secretory trafficking, we investigated its function in Golgi homeostasis. Here, we report that knockdown (KD) of cortactin leads to a dramatic change in Golgi morphology by light microscopy, dependent on binding the Arp2/3 actin‐nucleating complex. Surprisingly, there was little effect of cortactin‐KD on anterograde trafficking of the constitutive cargo vesicular stomatitis virus glycoprotein (VSVG), Golgi assembly from endoplasmic reticulum membranes upon Brefeldin A washout, or Golgi ultrastructure. Instead, electron microscopy studies revealed that cortactin‐KD cells contained a large number of immature‐appearing late endosomal/lysosomal (LE/Lys) hybrid organelles, similar to those found in lysosomal storage diseases. Consistent with a defect in LE/Lys trafficking, cortactin‐KD cells also exhibited accumulation of free cholesterol and retention of the retrograde Golgi cargo mannose‐6‐phosphate receptor in LE. Inhibition of LE maturation by treatment of control cells with Rab7 siRNA or chloroquine led to a compact Golgi morphology similar to that observed in cortactin‐KD cells. Furthermore, the Golgi morphology defects of cortactin‐KD cells could be rescued by removal of cholesterol‐containing lipids from the media, suggesting that buildup of cholesterol‐rich membranes in immature LE/Lys induced disturbances in retrograde trafficking. Taken together, these data reveal that LE/Lys maturation and trafficking are highly sensitive to cortactin‐regulated branched actin assembly and suggests that cytoskeletal‐induced Golgi morphology changes can be a consequence of altered trafficking at late endosomes. © 2012 Wiley Periodicals, Inc.