Spatio-temporal regulation and cleavage by matrix metalloproteinase stromelysin-3 implicate a role for laminin receptor in intestinal remodeling during Xenopus laevis metamorphosis.

The 37-kd laminin receptor precursor (LR) was first identified as a 67-kd protein that binds laminin with high affinity. We have recently isolated the Xenopus laevis LR as an in vitro substrate of matrix metalloproteinase stromelysin-3 (ST3), which is highly upregulated during intestinal metamorphosis in Xenopus laevis. Here, we show that LR is expressed in the intestinal epithelium of premetamorphic tadpoles. During intestinal metamorphosis, LR is downregulated in the apoptotic epithelium and concurrently upregulated in the connective tissue but with little expression in the developing adult epithelium. Toward the end of metamorphosis, as adult epithelial cells differentiate, they begin to express LR. Furthermore, LR is cleaved during intestinal remodeling when ST3 is highly expressed or in premetamorphic intestine of transgenic tadpoles overexpressing ST3. These results suggest that LR plays a role in cell fate determination and tissue morphogenesis, in part through its cleavage by ST3. Interestingly, high levels of LR are known to be expressed in tumor cells, which are often surrounded by fibroblasts expressing ST3, suggesting that LR cleavage by ST3 plays a role in both physiological and pathological processes.