Identification and Characterization of Cystatin-Related Epididymal and Spermatogenic (CRES) Expression in Anterior Pituitary Gonadotropes

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Title: Identification and Characterization of Cystatin-Related Epididymal and Spermatogenic (CRES) Expression in Anterior Pituitary Gonadotropes
Author: Sutton-Walsh, Heather Gayle
Abstract: Male factor infertility contributes to half of all infertility cases , yet current knowledge remains unable to diagnose all but gross abnormalities in male reproductive physiology . In an effort to identify proteins involved in initiating epididymal sperm maturation , our lab identified the cystatin -related epididymal spermatogenic (CRES ) gene based on its preferential expression in the initial epididymal segment . Cres represents a unique subgroup of the cystatin family of cysteine protease inhibitors in that its expression is restricted to reproductive tissues and its sequence predicts specificity distinct from classic cystatins . CRES protein is localized to the caput epididymal lumen and the sperm acrosome . Both compartments contain active proteases responsible for protein processing events that are required for sperm function ; however , the regulatory mechanisms controlling these processing events are poorly understood . These observations led to the proposal that CRES protein regulates protein processing in these tissues . We hypothesized that CRES might also regulate proteolysis in the pituitary gland for two reasons : (1 ) the pituitary gland expresses a number of proteases involved in preprotein processing ; and (2 ) the pituitary gland is functionally connected with the gonad via the hypothalamic -pituitary -gonadal axis . Thus , the goal of these studies was to determine whether CRES is expressed in the pituitary gland and if so , to examine its regulation by hypothalamic and /or gonadal factors . These studies demonstrate that CRES is expressed in the anterior pituitary gland and is co -localized intracellularly with leutinizing hormone (LH ) in gonadotrope secretory granules . To examine the regulation of Cres mRNA , we developed a semi -quantitative RT -PCR assay and showed that , unlike steroid hormones , GnRH is the primary physiologic regulator of Cres gene expression . Specifically , GnRH administration causes a rapid decrease in Cres mRNA levels , an effect opposite from its potent stimulation of LHp mRNA expression . In contrast , intracellular CRES and LHP protein levels were regulated similarly by steroid hormones , consistent with their being packaged within the same subset of secretory granules . Taken together , these studies indicate that CRES function is influenced by subtle alterations in the hypothalamic -pituitary -gonadal axis , suggesting it may regulate processing events important at specific times for gonadotrope secretory functions .
URI: http : / /hdl .handle .net /2346 /15256
Date: 2001-08

Citation

Identification and Characterization of Cystatin-Related Epididymal and Spermatogenic (CRES) Expression in Anterior Pituitary Gonadotropes. Doctoral dissertation, Texas Tech University. Available electronically from http : / /hdl .handle .net /2346 /15256 .

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