Plunc, a Member of the Secretory Gland Protein Family, Is Up-regulated in Nasal Respiratory Epithelium after Olfactory Bulbectomy

Abstract

Subtraction suppression hybridization was used with high throughput screening to identify transcripts of genes that are differentially expressed in nasal epithelium following lesioning of the olfactory bulb, termed bulbectomy. We isolated the rat homologue of plunc, a murine gene highly expressed in lung and nasopharyngeal regions, by this method. Rat plunc encodes a 270-amino acid protein containing a putative signal peptide. plunc up-regulation in respiratory epithelium was confirmed by Northern blot and in situ hybridization. plunc mRNA was expressed in nasal epithelium, heart, lung, thymus, and salivary gland in adult rodent. plunc was expressed in nasal epithelium, thymus, and salivary gland during embryogenesis. Antibodies against Plunc detected a 31-kDa protein in lung, heart, and spleen. Rat nasal epithelium displayed robust immunoreactivity that was highly localized to the microvilli layer of respiratory epithelium. The expression of plunc was up-regulated after bulbectomy in respiratory epithelium. We also detected secreted plunc in rat and human mucus. Sequence and homology analyses suggest that Plunc is a member of the secretory gland protein family with putative bactericidal/bacteriostatic function. This is the first protein found in respiratory epithelium whose expression is regulated by olfactory neuronal injury and may provide protection against infection subsequent to injury.