Fuller Maria, Mellett Natalie, Hein Leanne K, Brooks Doug A, Meikle Peter J
Genetics and Molecular Pathology, SA Pathology at Women's and Children's Hospital, North Adelaide, Australia; Department of Paediatrics, University of Adelaide, Australia.
Baker IDI Heart and Diabetes Institute, Melbourne, Australia.
Mol Genet Metab. 2015 Feb;114(2):268-73. doi: 10.1016/j.ymgme.2014.11.005. Epub 2014 Nov 12.
Fabry disease (FD) is an X-linked lysosomal storage disorder resulting from deficiency of α-galactosidase A (GLA). Traditionally, heterozygotes were considered asymptomatic carriers of FD, but it is now apparent that the asymptomatic female carrier is the exception and most heterozygotes suffer significant multisystemic disease. To determine why the process of cross-correction does not occur effectively in FD heterozygotes, we investigated GLA production and secretion in cultured skin fibroblasts as well as GLA levels in plasma. The maturation of GLA was similar in FD heterozygotes and control fibroblasts, confirming that both produce the 46kDa mature form; the same as that present in control plasma. However, the proportion of GLA secreted into the culture media was substantially less than eight other lysosomal proteins. Artificial generation of FD heterozygotes in cellulo, along with another lysosomal storage disorder, mucopolysaccharidosis type II, revealed no cross-correction in the FD system, whereas MPS II fibroblasts were able to cross-correct. In plasma, GLA was present as the 46kDa mature form, which lacks the mannose 6-phosphorylated moiety and is not able to be efficiently endocytosed by affected cells. Our evidence shows that fibroblasts secrete minimal amounts of GLA and consequently normal fibroblasts are unable to cross-correct FD fibroblasts. We suggest that symptomatic FD heterozygotes arise due to the secretion of primarily the mature form, with only small amounts of the mannose 6-phosphorylated form of GLA from unaffected cells. This limits capacity for enzyme cross correction of affected cells, despite uptake of exogenous recombinant GLA.
法布里病（FD）是一种X连锁溶酶体贮积症，由α-半乳糖苷酶A（GLA）缺乏所致。传统上，杂合子被认为是FD的无症状携带者，但现在很明显，无症状女性携带者是例外情况，大多数杂合子患有严重的多系统疾病。为了确定交叉校正过程在FD杂合子中为何不能有效发生，我们研究了培养的皮肤成纤维细胞中GLA的产生和分泌以及血浆中的GLA水平。FD杂合子和对照成纤维细胞中GLA的成熟情况相似，证实两者都产生46kDa的成熟形式，与对照血浆中的相同。然而，分泌到培养基中的GLA比例明显低于其他八种溶酶体蛋白。在细胞内人工生成FD杂合子，连同另一种溶酶体贮积症II型粘多糖病，结果显示FD系统中不存在交叉校正，而II型粘多糖病成纤维细胞能够进行交叉校正。在血浆中，GLA以46kDa的成熟形式存在，该形式缺乏甘露糖6-磷酸化部分，不能被受影响的细胞有效内吞。我们的证据表明，成纤维细胞分泌的GLA量极少，因此正常成纤维细胞无法对FD成纤维细胞进行交叉校正。我们认为，有症状的FD杂合子的出现是由于主要分泌成熟形式，而未受影响的细胞仅分泌少量甘露糖6-磷酸化形式的GLA。这限制了受影响细胞对酶交叉校正的能力，尽管摄取了外源性重组GLA。
