Iron plays many important roles in the brain, including involvement in myelination, neurotransmission and electron transfer in the respiratory chain. Transferrin (Tf), an iron transporter, is mainly biosynthesized in the liver, but can also be biosynthesized in the brain; i.e., by oligodendrocytes and the choroid plexus, a cerebrospinal fluid (CSF) producing tissue. The CSF contains two Tf isoforms, brain-type Tf and serum-type Tf, which differ in their glycan structures. Brain-type Tf is uniquely glycolsylated with biantennary asialo- and agalacto-complex type N-glycans that carry bisecting β1,4-GlcNAc and core α1,6-Fuc. The glycans of serum-type Tf in the CSF are similar to those of Tf in serum. Biochemical analyses reveal that the apparent molecular size of brain-type Tf is smaller than that of serum-type Tf, and that hydrophobic patches are exposed on brain-type Tf as demonstrated by hydrophobic probe binding studies. We found that brain-type Tf levels were decreased in idiopathic normal pressure hydrocephalus, in which CSF production is suspected to decrease, while brain-type Tf increased in spontaneous intracranial hypotension, in which CSF production is suspected to increase. These results suggest that brain-type Tf could be a biomarker of altered CSF production.

中文翻译：

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脑脊液中的转铁蛋白亚型及其与神经系统疾病的关系。

铁在大脑中扮演许多重要角色，包括参与呼吸链的髓鞘形成，神经传递和电子传递。转铁蛋白（Tf）是一种铁转运蛋白，主要在肝脏中生物合成，但也可以在大脑中生物合成；即通过少突胶质细胞和脉络丛，产生脑脊液（CSF）的组织。脑脊液包含两种Tf同工型，即脑型Tf和血清型Tf，它们的聚糖结构不同。脑型Tf独特地被双天线脱唾液酸和半乳糖复合物N型糖基糖基化，它们带有两等分的β1,4-GlcNAc和核心α1,6-Fuc。CSF中血清型Tf的聚糖与血清中Tf的聚糖相似。生化分析表明，脑型Tf的表观分子大小小于血清型Tf，疏水性探针结合研究表明，疏水性斑块暴露在脑型Tf上。我们发现，特发性正常压力脑积水的脑型Tf水平降低，怀疑是CSF产生减少，而自发性颅内低血压的脑型Tf升高，怀疑是CSF产生增加。这些结果表明脑型Tf可能是脑脊液产生改变的生物标志物。