KPL1, which encodes a novel PH domain-containing protein, is induced during ciliated cell differentiation of rat tracheal epithelial cells

Using differential display, we have identified a novel gene, KPL1, induced in rat tracheal epithelial (RTE) cells grown under conditions which stimula te ciliogenesis. The KPL1 protein is Predicted to contain a pleckstrin homo logy (PH) domain, which has been found in numerous signal transduction and cytoskeletal proteins. These domains are thought to function by recruiting proteins to cellular membranes, and they have been shown to bind phosphoino sitols and the beta/gamma subunit of G proteins. We have cloned rat and hum an KPL1; the predicted protein translations are 94% identical. Alternate tr anscripts exist in rat and human tracheal cells that predict a protein whic h contains a 35-amino acid insert. KPL1 was upregulated in RIE cultures und ergoing mucociliary but not squamous differentiation; and in cultures under going mucociliary differentiation, KPL1 expression most closely paralleled that of a marker of ciliated cell differentiation (axonemal dynein heavy ch ain) and not a marker of mucous cell differentiation (mucin 5AC). As a new member of the family of PH domain-containing proteins, KPL1 may have a uniq ue role in ciliated cell differentiation or function.