Starvation-induced lysosomal degradation of aldolase B requires glutamine 111 in a signal sequence for chaperone-mediated transport.
Starvation-induced lysosomal degradation of aldolase B requires glutamine 111 in a signal sequence for chaperone-mediated transport.
复制标题
饥饿诱导的醛缩酶 B 溶酶体降解需要信号序列中的谷氨酰胺 111 来进行分子伴侣介导的运输。
DOI：
10.1002/1097-4652(2001)9999:9999
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发表时间：
2001
影响因子：
5.6
通讯作者：
DunnJr,WA
中科院分区：
文献类型：
--
作者：
Susan,PP;DunnJr,WA
醛缩酶B是一种丰富的细胞质蛋白，存在于所有真核细胞中。像许多糖酵解酶一样，这种蛋白质在营养缺乏时被隔离到溶酶体中进行降解。我们在这里报道，重组醛缩酶B的降解在大鼠和人肝癌细胞缺乏氨基酸和血清的情况下增强了两倍。此外，饥饿诱导的醛缩酶B的降解被氯喹（一种溶酶体蛋白酶抑制剂）和3 -甲基腺嘌呤（一种自噬抑制剂）抑制。醛缩酶B有三个溶酶体靶向基序（Q12KKEL， Q58FREL和IKLDQ111），它们被认为与hsc73相互作用，从而启动其转运到溶酶体中。在这项研究中，我们突变了这些hsc73结合基序中必需的谷氨酰胺残基，以评估它们在饥饿期间醛缩酶B溶酶体降解中的作用。我们发现当谷氨酰胺12或58突变为天冬酰胺时，醛缩酶B的降解正常进行。然而，当谷氨酰胺111突变为天冬酰胺或苏氨酸时，饥饿诱导的降解被完全抑制。这些突变似乎没有改变醛缩酶B的三级结构，因为酶活性没有受到影响。我们的研究结果表明饥饿诱导的醛缩酶B的溶酶体降解需要自噬和谷氨酰胺111。我们讨论了自噬和hsc73介导的转运在醛缩酶b溶酶体分离中的可能作用©2001 Wiley‐Liss， Inc。
Aldolase B is an abundant cytosolic protein found in all eukaryotic cells. Like many glycolytic enzymes, this protein was sequestered into lysosomes for degradation during nutrient starvation. We report here that the degradation of recombinant aldolase B was enhanced two‐fold when rat and human hepatoma cells were starved for amino acid and serum. In addition, starvation‐induced degradation of aldolase B was inhibited by chloroquine, an inhibitor of lysosomal proteinases and by 3‐methyladenine, an inhibitor of autophagy. Aldolase B has three lysosomal targeting motifs (Q12KKEL, Q58FREL, and IKLDQ111) that have been proposed to interact with hsc73 thereby initiating its transport into lysosomes. In this study, we have mutated the essential glutamine residues in each of these hsc73‐binding motifs in order to evaluate their roles in the lysosomal degradation of aldolase B during starvation. We have found that when glutamines 12 or 58 are mutated to asparagines enhanced degradation of aldolase B proceeded normally. However, when glutamine 111 was mutated to an asparagine or a threonine, starvation‐induced degradation was completely suppressed. These mutations did not appear to alter the tertiary structure of aldolase B since enzymatic activity was not affected. Our results suggest that starvation‐induced lysosomal degradation of aldolase B requires both autophagy and glutamine 111. We discuss the possible roles for autophagy and hsc73‐mediated transport in the lysosomal sequestration of aldolase B. © 2001 Wiley‐Liss, Inc.