title: Bem3: Filling the GAP between cell polarity and secretion.
abstract: A highly conserved member of the Rho family of small GTPases, Cdc42 functions as the "master regulator of cell polarity." It has been reported that for proper establishment and maintenance of cell polarity, Cdc42 regulates and requires vesicle trafficking. Importantly, we recently discovered that in budding yeast, vesicle trafficking also controls the localization and function of Bem3, a GTPase activating protein for Cdc42. Specifically, we observed that Bem3 partitioned between the plasma membrane and an internal membrane-bound compartment. This Bem3-containing compartment was present during extended periods of apical growth, required actin tracks for trafficking to polarized sites and functioned as a recycling station that was positioned at the junction of endocytic and secretory pathways. Strikingly, many of these features are reminiscent of the Spitzenkörper, a dynamic structure involved in polarized growth during hyphal development in several filamentous fungi. Furthermore, Bem3 was not merely a passive cargo but actively recruited the secretory Rab GTPase Sec4 to this Spitzenkörper-like compartment. Importantly, this function of Bem3 was independent of its GAP activity. Our work demonstrates the existence of a complementary regulation between Bem3, a regulator of Cdc42 signaling and Sec4, a key component of the secretory machinery.
authors.affiliation: Department of Biological Sciences; Purdue University; West Lafayette, IN USA.
authors.forename: Arpita
authors.initials: A
authors.lastname: Sen
authors.affiliation: National Center for Biological Sciences; Bangalore, Karnataka India.
authors.forename: Debarati
authors.initials: D
authors.lastname: Mukherjee
authors.affiliation: Department of Biological Sciences; Purdue University; West Lafayette, IN USA.
authors.forename: R Claudio
authors.initials: RC
authors.lastname: Aguilar
keywords: Bem3; Spitzenkörper; cell polarity; recycling pathway; secretory pathway; vesicle trafficking
references.citation: J Cell Biol. 2004 Sep 13;166(6):889-900
references.pmid: 15353546
references.citation: Cold Spring Harb Perspect Biol. 2009 Sep;1(3):a003384
references.pmid: 20066112
references.citation: Mycol Res. 2006 Jan;110(Pt 1):4-13
references.pmid: 16378719
references.citation: Nature. 2002 Dec 12;420(6916):629-35
references.pmid: 12478284
references.citation: Cold Spring Harb Perspect Biol. 2009 Nov;1(5):a001321
references.pmid: 20066116
references.citation: Cell. 2007 Apr 20;129(2):411-22
references.pmid: 17448998
references.citation: Science. 2003 Feb 21;299(5610):1231-5
references.pmid: 12560471
references.citation: Mol Biol Cell. 2008 Apr;19(4):1439-49
references.pmid: 18216285
references.citation: J Cell Biol. 2001 Nov 12;155(4):581-92
references.pmid: 11706050
references.citation: Annu Rev Cell Dev Biol. 2005;21:247-69
references.pmid: 16212495
references.citation: Mol Biol Cell. 2011 Mar 1;22(5):624-33
references.pmid: 21209323
references.citation: Dev Cell. 2009 Dec;17(6):823-35
references.pmid: 20059952
references.citation: J Biol Chem. 1994 Jan 28;269(4):2369-72
references.pmid: 8300560
references.citation: J Cell Sci. 2013 Oct 15;126(Pt 20):4560-71
references.pmid: 23943876
references.citation: Nat Commun. 2013;4:1380
references.pmid: 23340420
references.citation: Protoplasma. 2003 Sep;222(1-2):53-9
references.pmid: 14513311
references.citation: J Biol Chem. 2001 Dec 14;276(50):46745-50
references.pmid: 11595741
references.citation: J Cell Sci. 2000 Feb;113 ( Pt 3):365-75
references.pmid: 10639324
references.citation: Nat Cell Biol. 2003 Apr;5(4):294-9
references.pmid: 12669083
references.citation: Antonie Van Leeuwenhoek. 2013 Apr;103(4):921-31
references.pmid: 23334442
references.citation: Proc Natl Acad Sci U S A. 2006 Mar 14;103(11):4116-21
references.pmid: 16537494
references.citation: Annu Rev Cell Dev Biol. 1999;15:365-91
references.pmid: 10611966
references.citation: Annu Rev Microbiol. 2013;67:587-609
references.pmid: 23808332
references.citation: J Cell Sci. 2004 Mar 15;117(Pt 8):1291-300
references.pmid: 15020669
references.citation: Eukaryot Cell. 2007 Mar;6(3):351-60
references.pmid: 17259546
references.citation: J Biol Chem. 2010 Oct 22;285(43):33073-33081
references.pmid: 20709745
references.citation: Microbiol Mol Biol Rev. 2007 Mar;71(1):48-96
references.pmid: 17347519
references.citation: Eukaryot Cell. 2002 Jun;1(3):469-80
references.pmid: 12455995
references.citation: Eukaryot Cell. 2005 Feb;4(2):225-9
references.pmid: 15701784