Mammalian homolog of Drosophila tumor suppressor lethal (2) giant larvae interacts with basolateral exocytic machinery in Madin-Darby canine kidney cells.
The Drosophila tumor suppressor protein lethal (2) giant larvae [l(2)gl] is involved in the establishment of epithelial cell polarity during development. Recently, a yeast homolog of the protein has been shown to interact with components of the post-Golgi exocytic machinery and to regulate a late step in protein secretion. Herein, we characterize a mammalian homolog of l(2)gl, called Mlgl, in the epithelial cell line Madin-Darby canine kidney (MDCK). Consistent with a role in cell polarity, Mlgl redistributes from a cytoplasmic localization to the lateral membrane after contact-naive MDCK cells make cell-cell contacts and establish a polarized phenotype. Phosphorylation within a highly conserved region of Mlgl is required to restrict the protein to the lateral domain, because a recombinant phospho-mutant is distributed in a nonpolar manner. Membrane-bound Mlgl from MDCK cell lysates was coimmunoprecipitated with syntaxin 4, a component of the exocytic machinery at the basolateral membrane, but not with other plasma membrane soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) proteins that are either absent from or not restricted to the basolateral membrane domain. These data suggest that Mlgl contributes to apico-basolateral polarity by regulating basolateral exocytosis.
Müsch
Anne
A
M. Dyson Vision Research Institute, Weill Medical College of Cornell University, New York, NY 10021, USA. amuesch@mail.med.cornell.edu
Cohen
David
D
Yeaman
Charles
C
Nelson
W James
WJ
Rodriguez-Boulan
Enrique
E
Brennwald
Patrick J
PJ
D016475:3T3 Cells; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D016764:Cell Polarity / Q000502:physiology*; D017124:Conserved Sequence; D004285:Dogs; D004330:Drosophila / Q000235:genetics; D029721:Drosophila Proteins; D004847:Epithelial Cells / Q000378:metabolism; D005089:Exocytosis / Q000502:physiology*; D005455:Fluorescent Antibody Technique; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007668:Kidney / Q000166:cytology; D008565:Membrane Proteins / Q000276:immunology / Q000378:metabolism; D051379:Mice; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D010641:Phenotype; D017434:Protein Structure, Tertiary; D050765:Qa-SNARE Proteins; D050600:SNARE Proteins; D025521:Tumor Suppressor Proteins; D033921:Vesicular Transport Proteins
D029721:Drosophila Proteins; D019476:Insect Proteins; D008565:Membrane Proteins; D050765:Qa-SNARE Proteins; D050600:SNARE Proteins; D025521:Tumor Suppressor Proteins; D033921:Vesicular Transport Proteins; C081435:l(2)gl protein, Drosophila