Cowley Darrin J, Chu Maylene, Gorr Sven Ulrik
Department of Periodontics, Endodontics and Dental Hygiene, University of Louisville Health Sciences Center, Louisville, KY 40292, USA.
Biochem Biophys Res Commun. 2002 Nov 22;299(1):98-101. doi: 10.1016/s0006-291x(02)02576-7.
Regulated secretory proteins are stored in secretory granules. While the sorting and storage process appears similar in endocrine and exocrine cells, the extent of overlap of sorting between endocrine and exocrine cell types is not clear. It is predicted that exocrine regulated secretory proteins that are stored with high efficiency in exocrine granules would also be stored efficiently in endocrine granules. To test this hypothesis, parotid secretory protein (PSP), which is stored efficiently in parotid acinar cells, was expressed in the endocrine cell lines GH4C1 and PC12. PSP undergoes stimulated secretion in both cell types. Secretion is similar to that of the endocrine regulated secretory protein chromogranin A but distinct from secreted alkaline phosphatase, a marker for the constitutive secretory pathway in endocrine cells. Subcellular fractionation of GH4C1 cells revealed that PSP co-fractionates with chromogranin A but not with secreted alkaline phosphatase.
受调控的分泌蛋白储存在分泌颗粒中。虽然在内分泌细胞和外分泌细胞中，分选和储存过程看起来相似，但内分泌细胞和外分泌细胞类型之间分选的重叠程度尚不清楚。据预测，能高效储存在外分泌颗粒中的外分泌受调控分泌蛋白也能高效储存在内分泌颗粒中。为了验证这一假设，在高效储存在腮腺腺泡细胞中的腮腺分泌蛋白（PSP）在GH4C1和PC12内分泌细胞系中表达。PSP在这两种细胞类型中均经历刺激分泌。其分泌类似于内分泌受调控分泌蛋白嗜铬粒蛋白A，但与分泌性碱性磷酸酶不同，后者是内分泌细胞组成型分泌途径的标志物。对GH4C1细胞进行亚细胞分级分离显示，PSP与嗜铬粒蛋白A共分级，但与分泌性碱性磷酸酶不共分级。
