Secreted glycoproteins serve a variety of functions related to cell–cell communication in developmental systems. We cloned LGL1, a novel glucocorticoid-inducible gene in foetal lung, and described its temporal and spatial localization in the rat. Disruption of foetal mesenchyme-specific LGL1 expression using antisense oligodeoxynucleotides, which was associated with a 50% decrease in lgl1 protein levels, inhibited airway epithelial branching in foetal rat gestational day 13 lung buds in explant culture. These findings suggested that lgl1 functions as a secreted signalling molecule. We now provide evidence supporting a role for lgl1 in mesenchymal–epithelial interactions that govern lung organogenesis. Lgl1 is a secreted glycoprotein with a conserved N-terminal secretory signal peptide. Using dual immunofluorescence, intracellular lgl1 was found to co-localize with markers of the Golgi apparatus and endoplasmic reticulum, consistent with its association with secretory vesicles. Using pulse–chase studies, we show that lgl1 is a stable protein with a half-life of 11.5 h. Furthermore, at gestational days 20 and 21 (term=22), foetal distal lung epithelial cells import lgl1 protein. Taken together, our findings support distinct roles for lgl1 as a mediator of glucocorticoid-induced mesenchymal–epithelial interactions in early and late foetal lung organogenesis.
- cysteine-rich secretory protein (CRISP)
- glucocorticoid-responsive gene
- lung development
- mesenchymal—epithelial interactions
- secreted factor
↵1 These authors contributed equally to this work.
Abbreviations used: CHO cell, Chinese-hamster ovary cell; β-COP, β-coatamer; CRISP, cysteine-rich secretory protein; DMEM, Dulbecco's modified Eagle's medium; EGFP, enhanced green fluorescent protein; ER, endoplasmic reticulum; FBS, foetal bovine serum; HBSS, Hank's balanced salt solution; HEK-293T cell, human embryonic kidney 293T cell; LGL1, late gestation lung 1 (LGL1 denotes the late gestation lung 1 gene; lgl1 denotes the late gestation lung 1 gene product); MEM, minimal essential medium; PNGase F, peptide N-glycosidase F.
- The Biochemical Society, London ©2003