title: LI-cadherin cis-dimerizes in the plasma membrane Ca(2+) independently and forms highly dynamic trans-contacts.
abstract: LI-cadherin belongs to the family of 7D-cadherins that is characterized by a low sequence similarity to classical cadherins, seven extracellular cadherin repeats (ECs), and a short cytoplasmic domain. Nevertheless, LI-cadherins mediates Ca(2+)-dependent cell-cell adhesion and induces an epitheloid cellular phenotype in non-polarized CHO cells. Whereas several studies suggest that classical cadherins cis-dimerize in a Ca(2+)-dependent manner and interact in trans by strand-swapping tryptophan 2 of EC1, little is known about the molecular interactions of LI-cadherin, which lacks tryptophan 2. We thus expressed fluorescent LI-cadherin fusion proteins in HEK293 and CHO cells, analyzed their cell-cell adhesive properties and studied their cellular distribution, cis-interaction, and lateral diffusion in the presence and absence of Ca(2+). LI-cadherin highly concentrates in cell contact areas but rapidly leaves those sites upon Ca(2+) depletion and redistributes evenly on the cell surface, indicating that it is only kept in the contact areas by trans-interactions. Fluorescence resonance energy transfer analysis of LI-cadherin-CFP and -YFP revealed that LI-cadherin forms cis-dimers that resist Ca(2+) depletion. As determined by fluorescence redistribution after photobleaching, LI-cadherin freely diffuses in the plasma membrane as a cis-dimer (D = 0.42 ± 0.03 μm(2)/s). When trapped by trans-binding in cell contact areas, its diffusion coefficient decreases only threefold to D = 0.12 ± 0.01 μm(2)/s, revealing that, in contrast to classical and desmosomal cadherins, trans-contacts formed by LI-cadherin are highly dynamic.
authors: Institute for Transfusion Medicine, Charité, Berlin, Germany.
authors: Thilo
authors: T
authors: Bartolmäs
authors: Caroline
authors: C
authors: Hirschfeld-Ihlow
authors: Sven
authors: S
authors: Jonas
authors: Michael
authors: M
authors: Schaefer
authors: Reinhard
authors: R
authors: Geßner
mesh_terms: D000818:Animals; D016466:CHO Cells; D015820:Cadherins / Q000737:chemistry* / Q000378:metabolism*; D002118:Calcium / Q000737:chemistry / Q000378:metabolism*; D002448:Cell Adhesion; D002460:Cell Line; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D006224:Cricetinae; D004058:Diffusion; D031541:Fluorescence Resonance Energy Transfer; D057809:HEK293 Cells; D006801:Humans; D011485:Protein Binding; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: D015820:Cadherins; D011993:Recombinant Fusion Proteins; D002118:Calcium