AP-3 mediates tyrosinase but not TRP-1 trafficking in human melanocytes
AP-3 mediates tyrosinase but not TRP-1 trafficking in human melanocytes
复制标题
DOI：
10.1091/mbc.12.7.2075
复制
发表时间：
2001-07-01
影响因子：
3.3
通讯作者：
Boissy, RE
中科院分区：
文献类型：
--
作者：
Huizing, M;Sarangarajan, R;Boissy, RE
Hermansky-Pudlak综合征2型（HPS-2）患者在衔接复合物-3（AP-3）的β 3A亚基中存在突变，并且该复合物存在功能缺陷。AP-3在新囊泡的形成中充当外壳蛋白，显然包括血小板的致密体和黑素细胞的黑素体。我们使用培养的HPS-2黑素细胞来确定AP-3在黑素生成蛋白酪氨酸酶和酪氨酸酶相关蛋白-1（TRP-1）运输中的作用。TRP-1在正常黑素细胞和HPS-2黑素细胞中均表现出典型的黑素小体模式。相比之下，酪氨酸酶表现出黑素体（即，核周和树突状）模式，但在HPS-2黑素细胞中仅为核周模式。此外，酪氨酸酶在用编码AP-3复合物的β 3A亚基的cDNA转染的HPS-2黑素细胞中表现出正常的表达模式。这表明AP-3在酪氨酸酶向前黑素体的正常运输中的作用，与酪氨酸酶分子的C-末端部分中存在的双亮氨酸识别信号一致。在AP-3缺陷细胞中，酪氨酸酶也存在于类似晚期内体或多泡体的结构中;这些囊泡含有缺乏酪氨酸酶的脱鞘。这表明，在正常情况下，AP-3可以作用于多泡体，形成含有酪氨酸酶的囊泡，与前黑素体融合。最后，我们的研究表明，酪氨酸酶和TRP-1使用不同的机制，以达到其premelanosomal目的地。
Patients with Hermansky-Pudlak syndrome type 2 (HPS-2) have mutations in the beta 3A subunit of adaptor complex-3 (AP-3) and functional deficiency of this complex. AP-3 serves as a coat protein in the formation of new vesicles, including, apparently, the platelet's dense body and the melanocyte's melanosome. We used HPS-2 melanocytes in culture to determine the role of AP-3 in the trafficking of the melanogenic proteins tyrosinase and tyrosinase-related protein-1 (TRP-1). TRP-1 displayed a typical melanosomal pattern in both normal and HPS-2 melanocytes. In contrast, tyrosinase exhibited a melanosomal (i.e., perinuclear and dendritic) pattern in normal cells but only a perinuclear pattern in the HPS-2 melanocytes. In addition, tyrosinase exhibited a normal pattern of expression in HPS-2 melanocytes transfected with a cDNA encoding the beta 3A subunit of the AP-3 complex. This suggests a role for AP-3 in the normal trafficking of tyrosinase to premelanosomes, consistent with the presence of a dileucine recognition signal in the C-terminal portion of the tyrosinase molecule. In the AP-3-deficient cells, tyrosinase was also present in structures resembling late endosomes or multivesicular bodies; these vesicles contained exvaginations devoid of tyrosinase. This suggests that, under normal circumstances, AP-3 may act on multivesicular bodies to form tyrosinase-containing vesicles destined to fuse with premelanosomes. Finally, our studies demonstrate that tyrosinase and TRP-1 use different mechanisms to reach their premelanosomal destination.