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* Institute of Clinical Chemistry and Biochemistry, Virchow-Hospital, Humboldt-University Berlin, Germany; The adhesive function of classical cadherins
depends on the association with cytoplasmic proteins,
termed catenins, which serve as a link between cadherins and the actin cytoskeleton. LI-cadherin, a structurally different member of the cadherin family, mediates Ca2+-dependent cell-cell adhesion, although its
markedly short cytoplasmic domain exhibits no homology to this highly conserved region of classical cadherins. We now examined whether the adhesive function of LI-cadherin depends on the interaction with
catenins, the actin cytoskeleton or other cytoplasmic
components. In contrast to classical cadherins, LI-cadherin, when expressed in mouse L cells, was neither associated with catenins nor did it induce an upregulation
of To analyze whether this function requires any interaction with proteins other than catenins, a glycosyl
phosphatidylinositol-anchored form of LI-cadherin
(LI-cadherinGPI) was constructed and expressed in
Drosophila S2 cells. The mutant protein was able to induce Ca2+-dependent, homophilic cell-cell adhesion,
and its adhesive properties were indistinguishable from
those of wild type LI-cadherin. These findings indicate
that the adhesive function of LI-cadherin is independent of any interaction with cytoplasmic components,
and consequently should not be sensitive to regulatory
mechanisms affecting the binding of classical cadherins
to catenins and to the cytoskeleton. Thus, we postulate
that the adhesive function of LI-cadherin is complementary to that of coexpressed classical cadherins ensuring cell-cell contacts even under conditions that downregulate the function of classical cadherins.
Department of
Biochemistry, University of Ulm, Germany, § Department of Anatomy and Cell Biology, University of Michigan, Ann Arbor,
Michigan 48109
-catenin. Consistent with these findings, LI-cadherin was not resistant to detergent extraction and did
not induce a reorganization of the actin cytoskeleton.
However, LI-cadherin was still able to mediate Ca2+dependent cell-cell adhesion.
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