Multiple mRNAs encode the avian lysosomal membrane protein LAMP-2, resulting in alternative transmembrane and cytoplasmic domains.
Multiple mRNAs encode the avian lysosomal membrane protein LAMP-2, resulting in alternative transmembrane and cytoplasmic domains.
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发表时间：
1995-05
影响因子：
4
通讯作者：
C. Hatem;N. Gough;D. Fambrough
中科院分区：
文献类型：
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作者：
C. Hatem;N. Gough;D. Fambrough
溶酶体膜富含广泛糖基化的跨膜蛋白LAMP-1和LAMP-2。LAMP-1蛋白已经从几种哺乳动物和鸡中得到了鉴定，但还没有描述LAMP-2的非哺乳动物同源物，也没有报道这两种蛋白的剪接变体。在此，我们报道了三个编码鸡LAMP-2的cDNA克隆的特征。CDNA的核苷酸序列在开放阅读框架内的3‘端有分歧，导致编码三个不同的跨膜区和细胞质结构域的序列。Southern分析表明，鸡LAMP-2的共同区域只有一个基因编码。分歧的位置和共同序列的同一性与3‘外显子的选择性剪接一致。对成年鸡组织中存在的mRNAs的分析表明，这三个鸡LAMP-2变体具有组织特异性表达，其中LAMP-2b主要在大脑中表达。LAMP类蛋白的胞质结构域包含将这些分子定向到溶酶体的靶向信号。利用由鸡LEP100(LAMP-1)的管腔结构域和LAMP-2变异体的跨膜和胞质结构域组成的嵌合体，我们在转基因小鼠L细胞中证明了所有三个LAMP-2羧基末端区域都能够将嵌合蛋白靶向溶酶体。在哺乳动物细胞中，LAMP蛋白的表达水平、亚细胞分布和糖基化都随着细胞分化而改变，并且在某些肿瘤细胞系中与转移潜能相关。LAMP-2转录本的选择性剪接可能在这些变化中发挥作用。
Lysosomal membranes are enriched in extensively glycosylated transmembrane proteins, LAMP-1 and LAMP-2. LAMP-1 proteins have been characterized from several mammalian species and from chickens, but no non-mammalian homologues of LAMP-2 have been described, and no splice variants of either protein have been reported. Here we report the characterization of three cDNA clones encoding chicken LAMP-2. The nucleotide sequences of the cDNAs diverge at their 3' ends within the open reading frame, resulting in sequences that code for three different transmembrane and cytoplasmic domains. Southern analysis suggests that a single gene encodes the common region of chicken LAMP-2. The position of the divergence and the identity of the common sequence are consistent with alternative splicing of 3' exons. Analysis of the mRNAs present in adult chicken tissues suggests tissue-specific expression of the three chicken LAMP-2 variants, with LAMP-2b expressed primarily in the brain. The cytoplasmic domain of LAMP-type proteins contains the targeting signal for directing these molecules to the lysosome. Using chimeras consisting of the lumenal domain of chicken LEP100 (a LAMP-1) and the transmembrane and cytoplasmic domains of the LAMP-2 variants, we demonstrate in transfected mouse L cells that all three LAMP-2 carboxyl-terminal regions are capable of targeting the chimeric proteins to lysosomes. Levels of expression, subcellular distribution, and glycosylation of the LAMP proteins have all been shown to change with differentiation in mammalian cells and to be correlated with metastatic potential in certain tumor cell lines. Alternative splicing of the LAMP-2 transcript may play a role in these changes.