45-KDa GTP-binding Protein from Rat Olfactory Epithelium: Purification, Characterization and Localization

Abstract

The rat olfactory epithelium contains a specific water-soluble 45-kDa protein. This protein is recognized by anti-peptide antibodies which react with alpha-subunits of the known G-proteins. The 45-kDa protein has been isolated using DEAE-chromatography and gel-exclusion chromatography. The content of 45-kDa protein is about 2% of the total soluble proteins of the olfactory mucosa and it is located at the mucociliary surface. According to photo-affinity labeling, the 45-kDa protein possesses a high affinity to GTP and exhibits low GTP hydrolytic activity. The functions of the 45-kDa protein are discussed.

Sec14l3 Is Specifically Expressed in Mouse Airway Ciliated Cells

“…These results are consistent with a previous report that the rat homologue of the Sec14l3 transcript is expressed in the surface layers of the trachea and in the ciliated bronchial epithelium in the lung [17]. The results of our ISH experiments extend the cell types known to express Sec14l3 from sustentacular cells of the olfactory mucosa [17,18] to include ciliated cells in lung bronchial/ bronchiolar epithelia (Fig. 2).…”

“…Indeed, sustentacular cells in the rat nasal mucosa secrete the 45-kDa Sec14l3 protein, which forms part of the extracellular matrix in the mucus layer of the mucociliary surface of rat olfactory epithelium [18]. Moreover, COS-1 cells transduced with a Sec14l3 expression vector similarly excrete the Sec14l3 protein into the culture medium [26].…”

“…Sec14l3 encodes a water-soluble 45-kDa secreted protein [17,18]. The Sec14l3 transcript is expressed in olfactory epithelium, the trachea, and bronchial epithelium in the lung [17].…”

A Proteomic Approach to Study of the Function of the Sec14P-Like p45 Protein

“…Subsequently, protein p45 had been isolated from the rat olfactory epithelium and identified as a GTP-binding protein, which also exhibits GTPase activity [2]. The content of protein p45 was shown to be about 2% of all water-soluble proteins of the olfactory epithelium.…”

“…The protein was detected at the highest concentrations in the surface layers of tissues that are in direct contact with environment [3]. Moreover, the protein was localized in secretory vesicles of cells of these tissues, as well as in the secretes released by cells into extracellular space [1][2][3]. Our experiments with the expression of p45 cDNA in COS-1 eukaryotic cells (unpublished data) indicated that protein p45 is accumulated in secretory vesicles and extracellular space, a culture medium for transfected cells.…”