Phyllis A. Shaw

Research

Hormonal regulation of genes encoding cysteine proteinase inhibitors (cystatins); regulation of cystatin gene expression during development.

Cysteine proteinases play an important role in the intracellular breakdown of collagen, bone resorption, the processing of prohormones and proenzymes, the penetration of tissue by bacteria and viruses, and tumor metastasis. These enzymes' activities are l argely determined by the levels of an evolutionary-related superfamily of inhibitor proteins called cystatins. Although these cysteine proteinase inhibitors inhibit cysteine proteinases in vitro, their in vivo functions and the mechanisms regulating them have not been demonstrated. This laboratory studies regulation of cystatin gene expression during development. Rat salivary glands provide a useful system for examining the regulation of cystatin genes by hormones and the autonomic nervous system. We have cloned and sequenced cDNA encoding a member of family 2 of mammalian cystatins, the secreted salivary cystatin (Cys S), and directly measured its in vitro cysteine proteinase inhibitory activity. The Cys S gene is expressed in the submandibular gland during the postnatal development of the rat; it is not expressed in submandibular glands of adult rats. The regulation of the rat Cys S gene by the autonomic nervous system is suggested by its inducibility in adult submandibular glands by the adrenoreceptor agonist isoproterenol (IPR). More recent in vivo studies suggest the participation of factor(s) from the sympathetic nervous system in the IPR-induced expression of the Cys S gene. To more carefully dissect the regulation of the Cys S gene, we have isolated and sequenced the complete gene, including 2 kb of 5'-flanking sequence and are beginning characterizations of the promoter region in vivo.

Significance: Rat cystatin S is highly homologous to low molecular weight human cystatins. Two human diseases are known to result directly from genetic alterations of cystatins: an autosomal dominant form of cerebral hemorrhagia in Icelandic patients and an autosomal recessive form of progressive myoclonus epilepsy.