Expression pattern and function of chitinase family proteins, endogenous lectins

几丁质酶家族蛋白质是对N-乙酰葡糖胺具有亲和力的内源性凝集素。在哺乳动物中发现了两个具有几丁质酶活性的成员，酸性哺乳动物几丁质酶（AMCase）和壳三糖苷酶，并对其细胞表达进行了研究。此外，我们选择了两个几丁质酶家族蛋白，没有几丁质酶活性，Ym和brp-39，并揭示了他们的表达位点。唾液和胃液中的腺泡细胞和胃主细胞的分泌颗粒中含有AMCase。另一方面，牛的AMCase在肝脏中产生并释放到血液中。泰勒虫感染引起的血中AMCase浓度的急剧增加表明其在抵抗病原菌和寄生虫感染中的作用。虽然人壳三糖苷酶在巨噬细胞和中性粒细胞中表达，但小鼠对应物在口腔复层上皮中表达，表明该几丁质酶的另一种功能。Ym 1在小鼠骨髓和脾脏中的早熟粒细胞中表达，而在成熟的中性粒细胞中消失。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包含在肺泡巨噬细胞中并分泌到肺泡腔中。感染M. Corti，表达Ym的炎性细胞聚集在肝脏中的寄生虫周围，而肺中含Ym的巨噬细胞数量增加并变为多核巨细胞。Brp-39在关节软骨内骨化处的软骨细胞和退化乳腺中的腺泡细胞中表达。由于哺乳期乳腺不表达brp-39，因此该几丁质酶可能参与乳腺退化或组织重建。

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.