Mammalian homolog of Drosophila tumor suppressor lethal (2) giant larvae interacts with basolateral exocytic machinery in Madin-Darby canine kidney cells

M. Dyson Vision Research Institute, Weill Medical College of Cornell University, New York, NY 10021, USA.
Molecular Biology of the Cell (Impact Factor: 4.47). 02/2002; 13(1):158-68. DOI: 10.1091/mbc.01-10-0496
Source: PubMed


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.

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    • "The Scribble complex, containing Lgl, Dlg, Scribble, establishes the basolateral membrane domain. Crb marks apical membranes [20], [21], [22], [23], [24], whilst Lgl2 localizes to basolateral membranes [23], [24], [25], [26] in Drosophila epithelia, cultured mammalian epithelial cells and Xenopus blastula presumptive epithelia. Crb and Lgl are conserved apical and basolateral membrane markers, respectively. "
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    ABSTRACT: During early vertebrate development, epithelial cells establish and maintain apicobasal polarity, failure of which can cause developmental defects or cancer metastasis. This process has been mostly studied in simple epithelia that have only one layer of cells, but is poorly understood in stratified epithelia. In this paper we address the role of the polarity protein Partitioning defective-6 homolog beta (Par6b) in the developing stratified epidermis of Xenopus laevis. At the blastula stage, animal blastomeres divide perpendicularly to the apicobasal axis to generate partially polarized superficial cells and non-polarized deep cells. Both cell populations modify their apicobasal polarity during the gastrula stage, before differentiating into the superficial and deep layers of epidermis. Early differentiation of the epidermis is normal in Par6b-depleted embryos; however, epidermal cells dissociate and detach from embryos at the tailbud stage. Par6b-depleted epidermal cells exhibit a significant reduction in basolaterally localized E-cadherin. Examination of the apical marker Crumbs homolog 3 (Crb3) and the basolateral marker Lethal giant larvae 2 (Lgl2) after Par6b depletion reveals that Par6b cell-autonomously regulates the dynamics of apicobasal polarity in both superficial and deep epidermal layers. Par6b is required to maintain the "basolateral" state in both epidermal layers, which explains the reduction of basolateral adhesion complexes and epidermal cells shedding.
    PLoS ONE 10/2013; 8(10):e76854. DOI:10.1371/journal.pone.0076854 · 3.23 Impact Factor
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    • "Lgl may target proteins to specific membrane locations by regulating vesicle trafficking. Lgl homologs in yeast (Sro7p and Sro77p) and mammals (Lgl1 and Lgl2) bind membrane t-SNAREs (target soluble N-ethylmaleimide attachment protein receptors) that mediate fusion of post-Golgi transport vesicles to target membranes (Lehman et al., 1999; Müsch et al., 2002), suggesting a link between Lgl and polarized exocytosis. Sro7p also interacts with the exocyst complex (Zhang et al., 2005), which tethers vesicles to the plasma membrane, and Sec4p (Grosshans et al., 2006), a member of the Rab family of GTPases that regulate vesicle trafficking and exocyst function. "
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    ABSTRACT: Motile cilia perform crucial functions during embryonic development and throughout adult life. Development of organs containing motile cilia involves regulation of cilia formation (ciliogenesis) and formation of a luminal space (lumenogenesis) in which cilia generate fluid flows. Control of ciliogenesis and lumenogenesis is not yet fully understood, and it remains unclear whether these processes are coupled. In the zebrafish embryo, lethal giant larvae 2 (lgl2) is expressed prominently in ciliated organs. Lgl proteins are involved in establishing cell polarity and have been implicated in vesicle trafficking. Here, we identified a role for Lgl2 in development of ciliated epithelia in Kupffer's vesicle, which directs left-right asymmetry of the embryo; the otic vesicles, which give rise to the inner ear; and the pronephric ducts of the kidney. Using Kupffer's vesicle as a model ciliated organ, we found that depletion of Lgl2 disrupted lumen formation and reduced cilia number and length. Immunofluorescence and time-lapse imaging of Kupffer's vesicle morphogenesis in Lgl2-deficient embryos suggested cell adhesion defects and revealed loss of the adherens junction component E-cadherin at lateral membranes. Genetic interaction experiments indicate that Lgl2 interacts with Rab11a to regulate E-cadherin and mediate lumen formation that is uncoupled from cilia formation. These results uncover new roles and interactions for Lgl2 that are crucial for both lumenogenesis and ciliogenesis and indicate that these processes are genetically separable in zebrafish.
    Development 04/2013; 140(7):1550-1559. DOI:10.1242/dev.087130 · 6.46 Impact Factor
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    • "The PAR proteins, plus several other polarity proteins including Lgl and the Cdc42 GTPase, have been implicated in control both of apical protein traffic and E-cadherin endocytosis from adherens junctions while, in a reciprocal fashion, vesicle sorting proteins, including several Rabs, are required for normal localization of the polarity proteins [1]–[4]. Although Par3 can bind to the exocyst complex [5], and Lgl associates with syntaxins [6], the underlying mechanisms for the interplay between these two machineries remain unclear. Scrb is required for clustering of synaptic vesicles at synapses [7], [8] and over-expressed Scrb, through a β-PIX:GIT1:ARF6 pathway, inhibits endocytosis of the thyroid stimulating hormone receptor (TSHR) and promotes recycling back to the plasma membrane [9]. "
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    ABSTRACT: Several polarity proteins, including Scribble (Scrb) have been implicated in control of vesicle traffic, and in particular the endocytosis of E-cadherin, but through unknown mechanisms. We now show that depletion of Scrb enhances endocytosis of E-cadherin by weakening the E-cadherin-p120catenin interaction. Unexpectedly, however, the internalized E-cadherin is not degraded but accumulates in the Golgi apparatus. Silencing p120-catenin causes degradation of E-cadherin in lysosomes, but degradation is blocked by the co-depletion of Scrb, which diverts the internalized E-cadherin to the Golgi. Loss of Scrb also enhances E-cadherin binding to retromer components, and retromer is required for Golgi accumulation of Scrb, and E-cadherin stability. These data identify a novel and unanticipated function for Scrb in blocking retromer-mediated diversion of E-cadherin to the Golgi. They provide evidence that polarity proteins can modify the intracellular itinerary for endocytosed membrane proteins.
    PLoS ONE 11/2012; 7(11):e51130. DOI:10.1371/journal.pone.0051130 · 3.23 Impact Factor
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