ANCHORING COMPLEX COMPONENTS LAMININ-5 AND TYPE-VII COLLAGEN IN INTESTINE - ASSOCIATION WITH MIGRATING AND DIFFERENTIATING ENTEROCYTES

Anchoring complex component laminin-5 and its subunits laminin (Ln)-al pha 3 and Ln-beta 3 chains, Type VII collagen, and integrin chains alp ha 3, alpha 6, and beta 4 were studied in developing and adult human i ntestine and compared with findings on Ln-alpha 1 and Ln-alpha 2 chain s. In adult human duodenum, jejunum, and ileum, Ln-5 detected with a p olyclonal antiserum and Ln-alpha 3 and Ln-beta 3 chains, detected with monoclonal antibodies (MAbs), were restricted to the epithelial basem ent membranes (BMs) of villi, whereas Ln-alpha 2 chain was seen only f ocally in crypt bottoms. In double labeling experiments, the stretch o f crypt BM corresponding to the proliferative cell compartment was fou nd to be devoid of both Ln-alpha 3 and Ln-alpha 2 chains. Double label ing for Ln-5 and proliferating cell nuclear antigen also showed an abr upt onset of Ln-5 expression exactly at the upper edge of the prolifer ative cell compartment, Type VII collagen was negligible in duodenum a nd showed a rising duodenal-ileal gradient localizing to villar BMs, D ouble labeling for Ln-5 and Type VII collagen, however, indicated only partial co-distribution in the intestine. Electron microscopy of ileu m revealed both anchoring filaments and anchoring fibrils but no hemid esmosomal plaques. Our results demonstrate the expression of Ln-5 in B Ms outside of stratified epithelia and indicate that Ln-5 in the intes tine is associated with the compartment of migrating and differentiati ng enterocytes. Absence of hemidesmosomes and the presence of other an choring complex components, such as Ln-5, Type VII collagen, and integ rin chains alpha 3, alpha 6, and beta 4, suggests unique properties fo r epithelial cell attachment in the intestine.