Microtubule plus-end and minus-end capture at adherens junctions is involved in the assembly of apico-basal arrays in polarised epithelial cells.
Apico-basal polarisation of epithelial cells involves a dramatic reorganisation of the microtubule cytoskeleton. The classic radial array of microtubules focused on a centrally located centrosome typical of many animal cells is lost or greatly reduced and a non-centrosomal apico-basal array develops. The molecules and mechanisms responsible for the assembly and positioning of these non-centrosomal microtubules have not been fully elucidated. Using a Nocodazole induced regrowth assay in invitro culture (MDCK) and in situ epithelial (cochlear Kolliker's) cell models we establish that the apico-basal array originates from the centrosome and that the non-centrosomal microtubule minus-end anchoring sites do not contribute significantly to their nucleation. Confocal and electron microscopy revealed that an extended radial array assembles with microtubule plus-ends targeting cadheren sites at adherens junctions and EB1 and CLIP-170 co-localising with beta-catenin and dynein clusters at the junction sites. The extended radial array is likely to be a vital intermediate step in the assembly process with cortical anchored dynein providing the mechanical force required for microtubule release, translocation and capture. Ultrastructural analyses of the apico-basal arrays in fully polarised MDCK and Kolliker's cells revealed microtubule minus-end association with the most apical adherens junction (Zonula adherens). We propose that a release and capture model involving both microtubule plus- and minus-end capture at adherens junctions is responsible for the generation of non-centrosomal apico-basal arrays in most centrosome containing polarised epithelial cells.
Bellett
Gemma
G
School of Biological Sciences, University of East Anglia, Norwich, NR4 7TJ, United Kingdom.
Carter
Jane M
JM
Keynton
Jennifer
J
Goldspink
Deborah
D
James
Colin
C
Moss
David K
DK
Mogensen
Mette M
MM
D022005:Adherens Junctions / Q000378:metabolism*; D000818:Animals; D015820:Cadherins / Q000378:metabolism; D002478:Cells, Cultured; D018385:Centrosome / Q000378:metabolism / Q000648:ultrastructure; D004285:Dogs; D004398:Dyneins / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism; D008870:Microtubules / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D015739:Nocodazole / Q000494:pharmacology; D050257:Tubulin Modulators / Q000378:metabolism
D015820:Cadherins; D050257:Tubulin Modulators; D004398:Dyneins; D015739:Nocodazole