Expression pattern and function of chitinase family proteins, endogenous lectins

几丁质酶家族蛋白是内源性凝集素，与n -乙酰氨基葡萄糖具有亲和力。在哺乳动物中发现了两种具有几丁质酶活性的成员：酸性哺乳动物几丁质酶（AMCase）和壳三酸苷酶（chitotriosidase），并对其细胞表达进行了研究。此外，我们选择了两个没有几丁质酶活性的几丁质酶家族蛋白Ym和brp-39，并揭示了它们的表达位点。AMCase分别存在于腮腺腺泡细胞和胃主细胞的分泌颗粒中，分泌于唾液和胃液中。另一方面，牛AMCase在肝脏中产生并释放到血液中。伊氏杆菌感染引起AMCase血药浓度急剧升高，提示其具有防御病原菌和寄生虫感染的作用。虽然人的几丁质苷酶在巨噬细胞和中性粒细胞中表达，但小鼠的几丁质苷酶在口腔的分层上皮中表达，这表明该几丁质酶具有另一种功能。Ym1在小鼠骨髓和脾脏的早熟中性粒细胞中表达，而在成熟中性粒细胞中消失。骨髓中的巨噬细胞也含有与细胞内针状晶体相关的Ym。在肺中，Ym被包含在肺泡巨噬细胞中，并分泌到肺泡间隙。在感染M. Corti的小鼠中，表达Ym的炎症细胞聚集在居住在肝脏的寄生虫周围，而肺中含有Ym的巨噬细胞数量增加并转变为多核巨细胞。Brp-39在关节软骨内成骨的软骨细胞和受缠乳腺的腺泡细胞中表达。由于哺乳期乳腺从未表达brp-39，该几丁质酶可能参与乳腺的复归或组织重建。

Chitinase family proteins are endogenous lectins which have affinity to N-acetylglucosamine. Two members with chitinase activity, acidic mammalian chitinase (AMCase) and chitotriosidase, have been identified in mammals, and their cellular expressions were investigated in the present study. Furthermore, we selected two chitinase family proteins without the chitinase activity, Ym and brp-39, and revealed their expression sites. AMCase was contained in secretory granules of parotid gland acinar cells and gastric chief cells, secreted in the saliva and gastric juice, respectively. Bovine AMCase, on the other hand, was produced in the liver and released into the blood. A sharp increase of blood AMCase concentration caused by Theileria infection suggested the role in defense against pathogenic bacterial and parasitic infection. Although human chitotriosidase is expressed in macrophages and neutrophils, the mouse counterpart was expressed in the stratified epithelium of oral cavity, suggesting another function of this chitinase. Ym1 was expressed in premature neutropluls in the bone marrow and spleen of mice, but disappeared in mature neutrophils. Macrohages in the bone marrow also contained Ym in association with intracellular needle-like crystals. In the lung, Ym was contained in alveolar macrophages and secreted into alveolar space. In mice infected with M. Corti, inflammatory cells expressing Ym gathered around the parasites residing in the liver, while Ym-containing macrophages in the lung increased in number and changed to multinudeated giant cells. Brp-39 was expressed by chondrocytes at the endochondral ossification of the joint, and by acinar cells in involuted mammary glands. Since mammary glands during lactation never expressed brp-39, this chitinase might be involved in the involution of mammary gland or tissue reconstruction.