Epithelial polarity requires septin coupling of vesicle transport to polyglutamylated microtubules

In epithelial cells, polarized growth and maintenance of apical and basolateral plasma membrane domains depend on protein sorting from the trans-Golgi network (TGN) and vesicle delivery to the plasma membrane. Septins are filamentous GTPases required for polarized membrane growth in budding yeast, but whether they function in epithelial polarity is unknown. Here, we show that in epithelial cells septin 2 (SEPT2) fibers colocalize with a subset of microtubule tracks composed of polyglutamylated (polyGlu) tubulin, and that vesicles containing apical or basolateral proteins exit the TGN along these SEPT2/polyGlu microtubule tracks. Tubulin-associated SEPT2 facilitates vesicle transport by maintaining polyGlu microtubule tracks and impeding tubulin binding of microtubule-associated protein 4 (MAP4). Significantly, this regulatory step is required for polarized, columnar-shaped epithelia biogenesis; upon SEPT2 depletion, cells become short and fibroblast-shaped due to intracellular accumulation of apical and basolateral membrane proteins, and loss of vertically oriented polyGlu microtubules. We suggest that septin coupling of the microtubule cytoskeleton to post-Golgi vesicle transport is required for the morphogenesis of polarized epithelia.

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Apiconuclear Organization of Microtubules Does Not Specify Protein Delivery from the Trans-Golgi Network to Different Membrane Domains in Polarized Epithelial Cells

Molecular Biology of the Cell ◽

10.1091/mbc.9.3.685 ◽

1998 ◽

Vol 9 (3) ◽

pp. 685-699 ◽

Cited By ~ 56

Author(s):

Kent K. Grindstaff ◽

Robert L. Bacallao ◽

W. James Nelson

Keyword(s):

Plasma Membrane ◽

Epithelial Cells ◽

Golgi Complex ◽

Apical Membrane ◽

Basolateral Membrane ◽

Membrane Domains ◽

Trans Golgi Network ◽

G Cells ◽

Polarized Epithelial Cells ◽

Golgi Network

In nonpolarized epithelial cells, microtubules originate from a broad perinuclear region coincident with the distribution of the Golgi complex and extend outward to the cell periphery (perinuclear [PN] organization). During development of epithelial cell polarity, microtubules reorganize to form long cortical filaments parallel to the lateral membrane, a meshwork of randomly oriented short filaments beneath the apical membrane, and short filaments at the base of the cell; the Golgi becomes localized above the nucleus in the subapical membrane cytoplasm (apiconuclear [AN] organization). The AN-type organization of microtubules is thought to be specialized in polarized epithelial cells to facilitate vesicle trafficking between the trans-Golgi Network (TGN) and the plasma membrane. We describe two clones of MDCK cells, which have different microtubule distributions: clone II/G cells, which gradually reorganize a PN-type distribution of microtubules and the Golgi complex to an AN-type during development of polarity, and clone II/J cells which maintain a PN-type organization. Both cell clones, however, exhibit identical steady-state polarity of apical and basolateral proteins. During development of cell surface polarity, both clones rapidly establish direct targeting pathways for newly synthesized gp80 and gp135/170, and E-cadherin between the TGN and apical and basolateral membrane, respectively; this occurs before development of the AN-type microtubule/Golgi organization in clone II/G cells. Exposure of both clone II/G and II/J cells to low temperature and nocodazole disrupts >99% of microtubules, resulting in: 1) 25–50% decrease in delivery of newly synthesized gp135/170 and E-cadherin to the apical and basolateral membrane, respectively, in both clone II/G and II/J cells, but with little or no missorting to the opposite membrane domain during all stages of polarity development; 2) ∼40% decrease in delivery of newly synthesized gp80 to the apical membrane with significant missorting to the basolateral membrane in newly established cultures of clone II/G and II/J cells; and 3) variable and nonspecific delivery of newly synthesized gp80 to both membrane domains in fully polarized cultures. These results define several classes of proteins that differ in their dependence on intact microtubules for efficient and specific targeting between the Golgi and plasma membrane domains.

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Essential function of Drosophila Sec6 in apical exocytosis of epithelial photoreceptor cells

The Journal of Cell Biology ◽

10.1083/jcb.200410081 ◽

2005 ◽

Vol 169 (4) ◽

pp. 635-646 ◽

Cited By ~ 79

Author(s):

Slobodan Beronja ◽

Patrick Laprise ◽

Ophelia Papoulas ◽

Milena Pellikka ◽

John Sisson ◽

...

Keyword(s):

Plasma Membrane ◽

Protein Transport ◽

Basolateral Membrane ◽

Photoreceptor Cells ◽

Secretory Vesicles ◽

Membrane Domains ◽

Animal Cells ◽

Light Sensing ◽

Membrane Growth ◽

Essential Function

Polarized exocytosis plays a major role in development and cell differentiation but the mechanisms that target exocytosis to specific membrane domains in animal cells are still poorly understood. We characterized Drosophila Sec6, a component of the exocyst complex that is believed to tether secretory vesicles to specific plasma membrane sites. sec6 mutations cause cell lethality and disrupt plasma membrane growth. In developing photoreceptor cells (PRCs), Sec6 but not Sec5 or Sec8 shows accumulation at adherens junctions. In late PRCs, Sec6, Sec5, and Sec8 colocalize at the rhabdomere, the light sensing subdomain of the apical membrane. PRCs with reduced Sec6 function accumulate secretory vesicles and fail to transport proteins to the rhabdomere, but show normal localization of proteins to the apical stalk membrane and the basolateral membrane. Furthermore, we show that Rab11 forms a complex with Sec5 and that Sec5 interacts with Sec6 suggesting that the exocyst is a Rab11 effector that facilitates protein transport to the apical rhabdomere in Drosophila PRCs.

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Apical protein transport and lumen morphogenesis in polarized epithelial cells

Bioscience Reports ◽

10.1042/bsr20100119 ◽

2011 ◽

Vol 31 (4) ◽

pp. 245-256 ◽

Cited By ~ 9

Author(s):

Carly Willenborg ◽

Rytis Prekeris

Keyword(s):

Epithelial Cells ◽

Protein Transport ◽

Three Dimensional ◽

Dimensional Structure ◽

Asymmetric Distribution ◽

Epithelial Polarity ◽

Membrane Domains ◽

Basolateral Plasma Membrane ◽

Junctional Complexes

Segregation of the apical and basolateral plasma membrane domains is the key distinguishing feature of epithelial cells. A series of interrelated cues and processes follow this primary polarization event, resulting in the morphogenesis of the mammalian epithelium. This review focuses on the role of the interactions between the extracellular matrix and neighbouring cells during the initiation and establishment of epithelial polarity, and the role that membrane transport and polarity complexes play in this process. An overview of the formation of the apical junctional complexes is given in relation to the generation of distinct membrane domains characterized by the asymmetric distribution of phosphoinositides and proteins. The mechanisms and machinery utilized by the trafficking pathways involved in the generation and maintenance of this apical-basolateral polarization are expounded, highlighting processes of apical-directed transport. Furthermore, the current proposed mechanisms for the organization of entire networks of cells into a structured, polarized three-dimensional structure are described, with an emphasis on the proposed mechanisms for the formation and expansion of the apical lumen.

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Protein-Mediated Inward Translocation of Phospholipids Occurs in both the Apical and Basolateral Plasma Membrane Domains of Epithelial Cells†

Biochemistry ◽

10.1021/bi981244n ◽

1999 ◽

Vol 38 (1) ◽

pp. 142-150 ◽

Cited By ~ 27

Author(s):

Thomas Pomorski ◽

Andreas Herrmann ◽

Peter Müller ◽

Gerrit van Meer ◽

Koert Burger

Keyword(s):

Plasma Membrane ◽

Epithelial Cells ◽

Membrane Domains ◽

Basolateral Plasma Membrane ◽

Plasma Membrane Domains

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Rab13 regulates membrane trafficking between TGN and recycling endosomes in polarized epithelial cells

The Journal of Cell Biology ◽

10.1083/jcb.200802176 ◽

2008 ◽

Vol 182 (5) ◽

pp. 845-853 ◽

Cited By ~ 74

Author(s):

Rita L. Nokes ◽

Ian C. Fields ◽

Ruth N. Collins ◽

Heike Fölsch

Keyword(s):

Plasma Membrane ◽

Epithelial Cells ◽

Membrane Trafficking ◽

Basolateral Membrane ◽

Dominant Negative ◽

Bronchial Epithelial ◽

Recycling Endosomes ◽

Cargo Proteins ◽

Vesicular Stomatitis ◽

Golgi Network

To maintain polarity, epithelial cells continuously sort transmembrane proteins to the apical or basolateral membrane domains during biosynthetic delivery or after internalization. During biosynthetic delivery, some cargo proteins move from the trans-Golgi network (TGN) into recycling endosomes (RE) before being delivered to the plasma membrane. However, proteins that regulate this transport step remained elusive. In this study, we show that Rab13 partially colocalizes with TGN38 at the TGN and transferrin receptors in RE. Knockdown of Rab13 with short hairpin RNA in human bronchial epithelial cells or overexpression of dominant-active or dominant-negative alleles of Rab13 in Madin-Darby canine kidney cells disrupts TGN38/46 localization at the TGN. Moreover, overexpression of Rab13 mutant alleles inhibits surface arrival of proteins that move through RE during biosynthetic delivery (vesicular stomatitis virus glycoprotein [VSVG], A-VSVG, and LDLR-CT27). Importantly, proteins using a direct route from the TGN to the plasma membrane are not affected. Thus, Rab13 appears to regulate membrane trafficking between TGN and RE.

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Polarized biosynthetic traffic in renal epithelial cells: sorting, sorting, everywhere

AJP Renal Physiology ◽

10.1152/ajprenal.00161.2006 ◽

2006 ◽

Vol 291 (4) ◽

pp. F707-F713 ◽

Cited By ~ 31

Author(s):

Mark A. Ellis ◽

Beth A. Potter ◽

Kerry O. Cresawn ◽

Ora A. Weisz

Keyword(s):

Epithelial Cells ◽

Biosynthetic Pathway ◽

Basolateral Membrane ◽

Proper Function ◽

Membrane Domains ◽

Conventional Model ◽

Recycling Endosomes ◽

Sorting Signals ◽

Vesicular Carriers ◽

Golgi Network

The maintenance of apical and basolateral membrane domains with distinct protein and lipid compositions is necessary for the proper function of polarized epithelial cells. Delivery of cargo to the basolateral surface is thought to be mediated by the interaction of cytoplasmically disposed sorting signals with sorting receptors, whereas apically destined cargoes are sorted via mechanisms dependent on cytoplasmic, glycan-mediated, or lipid-interacting sorting signals. Apical and basolateral cargo are delivered to the surface in discrete tubular and vesicular carriers that bud from the trans-Golgi network (TGN). While it has long been thought that the TGN is the primary compartment in which apical and basolateral cargoes are segregated, recent studies suggest that sorting may begin earlier along the biosynthetic pathway. Moreover, rather than being delivered directly from the TGN to the cell surface, at least a subset of biosynthetic cargo appears to transit recycling endosomes en route to the plasma membrane. The implications and limitations of these challenges to the conventional model for how proteins are sorted and trafficked along the biosynthetic pathway are discussed.

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Membrane microdomains: lessons from microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100140257 ◽

1995 ◽

Vol 53 ◽

pp. 776-777

Author(s):

J.M. Robinson ◽

J.M Oliver

Keyword(s):

Spatial Distribution ◽

Plasma Membrane ◽

Epithelial Cells ◽

Plasma Membranes ◽

Cell Types ◽

Imaging Modalities ◽

Membrane Microdomains ◽

Membrane Domains ◽

Lateral Heterogeneity ◽

Functional Importance

Specialized regions of plasma membranes displaying lateral heterogeneity are the focus of this Symposium. Specialized membrane domains are known for certain cell types such as differentiated epithelial cells where lateral heterogeneity in lipids and proteins exists between the apical and basolateral portions of the plasma membrane. Lateral heterogeneity and the presence of microdomains in membranes that are uniform in appearance have been more difficult to establish. Nonetheless a number of studies have provided evidence for membrane microdomains and indicated a functional importance for these structures.This symposium will focus on the use of various imaging modalities and related approaches to define membrane microdomains in a number of cell types. The importance of existing as well as emerging imaging technologies for use in the elucidation of membrane microdomains will be highlighted. The organization of membrane microdomains in terms of dimensions and spatial distribution is of considerable interest and will be addressed in this Symposium.

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Albumin binding of unconjugated [3H]bilirubin and its uptake by rat liver basolateral plasma membrane vesicles

Biochemical Journal ◽

10.1042/bj3160999 ◽

1996 ◽

Vol 316 (3) ◽

pp. 999-1004 ◽

Cited By ~ 19

Author(s):

Lorella PASCOLO ◽

Savino DEL VECCHIO ◽

Ronald K. KOEHLER ◽

J. Enrique BAYON ◽

Cecile C. WEBSTER ◽

...

Keyword(s):

Plasma Membrane ◽

Rat Liver ◽

Basolateral Membrane ◽

Membrane Vesicles ◽

Plasma Membrane Vesicles ◽

Experimental Conditions ◽

Saturation Kinetics ◽

Basolateral Plasma Membrane ◽

Component C ◽

Uptake Studies

Using highly purified unconjugated [3H]bilirubin (UCB), we measured UCB binding to delipidated human serum albumin (HSA) and its uptake by basolateral rat liver plasma membrane vesicles, in both the absence and presence of an inside-positive membrane potential. Free UCB concentrations ([Bf]) were calculated from UCB–HSA affinity constants (K´f), determined by five cycles of ultrafiltration through a Centricon-10 device (Amicon) of the same solutions used in the uptake studies. At HSA concentrations from 12 to 380 μM, K´f (litre/mol) was inversely related to [HSA], irrespective of the [Bt]/[HSA] ratio. K´f was 2.066×106+(3.258×108/[HSA]). When 50 mM KCl was iso-osmotically substituted for sucrose, the K´f value was significantly lower {2.077×106+(1.099×108/[HSA])}. The transport occurred into an osmotic-sensitive space. Below saturation ([Bf] ⩽ 65 nM), both electroneutral and electrogenic components followed saturation kinetics with respect to [Bf], with Km values of 28±7 and 57±8 nM respectively (mean±S.D., n = 3, P < 0.001). The Vmax was greater for the electrogenic than for the electroneutral component (112±12 versus 45±4 pmol of UCB·mg-1 of protein·15 s-1, P < 0.001). Sulphobromophthalein trans-stimulated both electrogenic (61%) and electroneutral (72%) UCB uptake. These data indicate that: (a) as [HSA] increases, K´f decreases, thus increasing the concentration of free UCB. This may account for much of the enhanced hepatocytic uptake of organic anions observed with increasing [HSA]. (b) UCB is taken up at the basolateral membrane of the hepatocyte by two systems with Km values within the range of physiological free UCB levels in plasma. The electrogenic component shows a lower affinity and a higher capacity than the electroneutral component. (c) It is important to calculate the actual [Bf] using a K´f value determined under the same experimental conditions (medium and [HSA]) used for the uptake studies.

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Investigation of the role of microtubules in protein secretion from lactating mouse mammary epithelial cells

Journal of Cell Science ◽

10.1242/jcs.102.2.239 ◽

1992 ◽

Vol 102 (2) ◽

pp. 239-247 ◽

Cited By ~ 2

Author(s):

M.E. Rennison ◽

S.E. Handel ◽

C.J. Wilde ◽

R.D. Burgoyne

Keyword(s):

Plasma Membrane ◽

Epithelial Cells ◽

Protein Secretion ◽

Secretory Pathway ◽

Mammary Epithelial Cells ◽

Early Stage ◽

Major Effect ◽

Vesicle Transport ◽

Mammary Epithelial ◽

Mammary Cells

Disruption of microtubules has been shown to reduce protein secretion from lactating mammary epithelial cells. To investigate the involvement of microtubules in the secretory pathway in these cells we have examined the effect of nocodazole on protein secretion from mammary epithelial cells derived from the lactating mouse. Mouse mammary cells have extensive microtubule networks and 85% of their tubulin was in a polymeric form. Treatment with 1 micrograms/ml nocodazole converted most of the tubulin into a soluble form. In a continuous labelling protocol it was found that nocodazole did not interfere with protein synthesis but over a 5 h period secretion was markedly inhibited. To determine whether the inhibition was at the level of early or late stages of the secretory pathway mammary cells were pulse-labelled for 1 h to label protein throughout the secretory pathway before nocodazole treatment. When secretion was subsequently assayed it was found to be slower and only partially inhibited. These findings suggest that the major effect of nocodazole is on an early stage of the secretory pathway and that microtubules normally facilitate vesicle transport to the plasma membrane. An involvement of microtubules in vesicle transport to the plasma membrane is consistent with an observed accumulation of casein vesicles in nocodazole-treated cells. Exocytosis stimulated by the calcium ionophore ionomycin was unaffected by nocodazole treatment. We conclude from these results that the major effect of nocodazole is at an early stage of the secretory pathway, one possible target being casein vesicle biogenesis in the trans-Golgi network.

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Putative linear motifs mediate the trafficking to apical and basolateral membranes

10.1101/2020.07.13.200501 ◽

2020 ◽

Author(s):

Laszlo Dobson ◽

András Zeke ◽

Levente Szekeres ◽

Tamás Langó ◽

Gábor Tusnády

Keyword(s):

Epithelial Cells ◽

Drug Transport ◽

Basolateral Membrane ◽

Transmembrane Proteins ◽

Transport Processes ◽

Membrane Domains ◽

Protein Distribution ◽

Basolateral Membranes ◽

Linear Motifs ◽

Cellular Components

AbstractCell polarity refers to the asymmetric organisation of cellular components in various cells. Epithelial cells are the best known examples of polarized cells, featuring apical and basolateral membrane domains. Despite huge efforts, the exact rules governing the protein distribution in such domains are still elusive. In this study we examined linear motifs accumulating in these parts and based on the results we prepared ‘Classical’ and Convolutional Neural Networks to classify human transmembrane proteins localizing into apical/basolateral membranes. Asymmetric expression of drug transporters results in vectorial drug transport, governing the pharmacokinetics of numerous substances, yet the data on how proteins are sorted in epithelial cells is very scattered. The provided dataset may offer help to experimentalists to characterize novel molecular targets to regulate transport processes more precisely.

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