Yadavalli Sivaramakrishna, Nadimpalli Siva Kumar
Protein Biochemistry and Molecular Biology Laboratory, Department of Biochemistry, University of Hyderabad, Hyderabad, 500 046, India.
Glycoconj J. 2008 Dec;25(9):889-901. doi: 10.1007/s10719-008-9153-5. Epub 2008 Jul 6.
Mammalian mannose 6-phosphate receptors (MPR 300 and 46) mediate transport of lysosomal enzymes to lysosomes. Recent studies established that the receptors are conserved throughout vertebrates. Although we purified the mollusc receptors and identified only a lysosomal enzyme receptor protein (LERP) in the Drosophila melanogaster, little is known about their structure and functional roles in the invertebrates. In the present study, we purified the putative receptors from the highly evolved invertebrate, starfish, cloned the cDNA for the MPR 46, and expressed it in mpr((-/-)) mouse embryonic fibroblast cells. Structural comparison of starfish receptor sequences with other vertebrate receptors gave valuable information on its extensive structural homology with the vertebrate MPR 46 proteins. The expressed protein efficiently sorts lysosomal enzymes within the cells establishing a functional role for this protein. This first report on the invertebrate MPR 46 further confirms the structural and functional conservation of the receptor not only in the vertebrates but also in the invertebrates.
哺乳动物的甘露糖6-磷酸受体（MPR 300和46）介导溶酶体酶向溶酶体的转运。最近的研究表明，这些受体在整个脊椎动物中都是保守的。尽管我们纯化了软体动物的受体，并在黑腹果蝇中仅鉴定出一种溶酶体酶受体蛋白（LERP），但对于它们在无脊椎动物中的结构和功能作用却知之甚少。在本研究中，我们从高度进化的无脊椎动物海星中纯化了假定的受体，克隆了MPR 46的cDNA，并在mpr（-/-）小鼠胚胎成纤维细胞中进行了表达。将海星受体序列与其他脊椎动物受体进行结构比较，为其与脊椎动物MPR 46蛋白的广泛结构同源性提供了有价值的信息。所表达的蛋白在细胞内有效地分选溶酶体酶，确立了该蛋白的功能作用。这篇关于无脊椎动物MPR 46的首次报道进一步证实了该受体不仅在脊椎动物中，而且在无脊椎动物中都具有结构和功能上的保守性。
