HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 296/6/L1019    most recent 90596.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Kolla, V. Articles by Ballard, P. L. PubMed PubMed Citation Articles by Kolla, V. Articles by Ballard, P. L.

Carcinoembryonic cell adhesion molecule 6 in human lung: regulated expression of a multifunctional type II cell protein

¹Department of Pediatrics and ²Department of Anesthesiology and Critical Care Medicine, Children's Hospital of Philadelphia and ³Institute for Environmental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania; and ⁴Department of Pediatrics, University of California, San Francisco, California

Submitted 2 December 2008 ; accepted in final form 23 March 2009

Carcinoembryonic cell adhesion molecule 6 (CEACAM6) is a glycosylated, glycosylphosphatidylinositol (GPI)-anchored protein expressed in epithelial cells of various human tissues. It binds gram-negative bacteria and is overexpressed in cancers, where it is antiapoptotic and promotes metastases. To characterize CEACAM6 expression in developing lung, we cultured human fetal lung epithelial cells and examined responses to differentiation-promoting hormones, adenovirus expressing thyroid transcription factor-1 (TTF-1), and silencing of TTF-1 with small inhibitory RNA. Glucocorticoid and cAMP had additive stimulatory effects on CEACAM6 content, and combined treatment maximally increased transcription rate, mRNA, and protein 10-fold. Knockdown of TTF-1 reduced hormone induction of CEACAM6 by 80%, and expression of recombinant TTF-1 increased CEACAM6 in a dose-dependent fashion. CEACAM6 content of lung tissue increased during the third trimester and postnatally. By immunostaining, CEACAM6 was present in fetal type II cells, but not mesenchymal cells, and localized to both the plasma membrane and within surfactant-containing lamellar bodies. CEACAM6 was secreted from cultured type II cells and was present in both surfactant and supernatant fractions of infant tracheal aspirates. In functional studies, CEACAM6 reduced inhibition of surfactant surface properties by proteins in vitro and blocked apoptosis of electroporated cultured cells. We conclude that CEACAM6 in fetal lung epithelial cells is developmentally and hormonally regulated and a target protein for TTF-1. Because CEACAM6 acts as an antiapoptotic factor and stabilizes surfactant function, in addition to a putative role in innate defense against bacteria, we propose that it is a multifunctional alveolar protein.

alveolar type II cells; thyroid transcription factor-1; glucocorticoid; adenosine 3',5'-cyclic monophosphate; apoptosis; surfactant