It depends on the hinge: a structure-functional analysis of galectin-8, a tandem-repeat type lectin.
Galectin-8, a member of the galectin family of mammalian lectins, is made of two carbohydrate-recognition domains (CRDs), joined by a "hinge" region. Ligation of integrins by galectin-8 induces a distinct cytoskeletal organization, associated with activation of the extracellular-regulated kinase (ERK) and phosphatidylinositol 3-kinase signaling cascades. We show that these properties of galectin-8 are mediated by the concerted action of its two CRDs and involve both protein-sugar and protein-protein interactions. Accordingly, the isolated N- or C-CRD domains of galectin-8 or galectin-8 mutated at selected residues implicated in sugar binding (E251Q; W85Y, W248Y, W[85,248]Y) exhibited reduced sugar binding, which was accompanied by severe impairment in the capacity of these mutants to promote the adhesive, spreading, and signaling functions of galectin-8. Other mutations that did not impair sugar binding (e.g. E88Q) still impeded the signaling and cell-adherence functions of galectin-8. Deletion of the "hinge" region similarly impaired the biological effects of galectin-8. These results provide evidence that cooperative interactions between the two CRDs and the "hinge" domain are required for the proper functioning of galectin-8.
Levy
Yifat
Y
Department of Chemical Services, The Weizmann Institute of Science, Rehovot 76100, Israel.
Auslender
Sofia
S
Eisenstein
Miriam
M
Vidavski
Roee R
RR
Ronen
Denise
D
Bershadsky
Alexander D
AD
Zick
Yehiel
Y
D000818:Animals; D016466:CHO Cells; D002448:Cell Adhesion / Q000502:physiology*; D048430:Cell Shape / Q000502:physiology; D006224:Cricetinae; D003412:Cricetulus; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005690:Galactose / Q000378:metabolism; D037161:Galectins / Q000235:genetics / Q000502:physiology*; D006384:Hemagglutination / Q000502:physiology; D009154:Mutation; D010766:Phosphorylation; D011485:Protein Binding; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
D037161:Galectins; D011994:Recombinant Proteins; D048049:Extracellular Signal-Regulated MAP Kinases; D005690:Galactose