Department of Medical Chemistry, Biochemistry and Biotechnology, University of Milan, F.lli Cervi 93, Segrate, Milan 20090, Italy.
J Cell Biochem. 2013 Jan;114(1):204-11. doi: 10.1002/jcb.24355.
The sialylation level of molecules, sialoglycoproteins and gangliosides, protruding from plasma membranes regulates multiple facets of erythrocyte function, from interaction with endothelium to cell lifespan. Our results demonstrate that: (a) Both sialidases NEU1 and NEU3 are present on erythrocyte plasma membrane; (b) NEU1 is kept on the plasma membrane in absence of the protective protein/cathepsin A (PPCA); (c) NEU1 and NEU3 are retained on the plasma membrane, as peripheral proteins, associated to the external leaflet and released by alkaline treatments; (d) NEU1 and NEU3 are segregated in Triton X-100 detergent-resistant membrane domains (DRMs); (e) NEU3 shows activity also at neutral pH; and (f) NEU1 and NEU3 are progressively lost during erythrocyte life. Interestingly, sialidase activity released from erythrocyte membranes after an alkaline treatment preserves its functionality and recognizes sialoglycoproteins and gangliosides. On the other hand, the weak anchorage of sialidases to the plasma membrane and their loss during erythrocyte life could be a tool to preserve the cellular sialic acid content in order to avoid the early ageing of erythrocyte and processes of cell aggregation in the capillaries.
分子、唾液糖蛋白和神经节苷脂的唾液酸化水平从与内皮细胞的相互作用到细胞寿命，调节着红细胞功能的多个方面。我们的结果表明：(a) 红细胞质膜上存在唾液酸酶 NEU1 和 NEU3；(b) 在缺乏保护性蛋白/组织蛋白酶 A (PPCA) 的情况下，NEU1 保留在质膜上；(c) NEU1 和 NEU3 作为外周蛋白与质膜的外小叶结合，并通过碱性处理释放；(d) NEU1 和 NEU3 被分隔在 Triton X-100 去污剂抗性膜域 (DRMs) 中；(e) NEU3 在中性 pH 下也具有活性；(f) 红细胞寿命过程中，NEU1 和 NEU3 逐渐丢失。有趣的是，碱性处理后从红细胞膜释放的唾液酸酶具有其功能，可识别唾液糖蛋白和神经节苷脂。另一方面，唾液酸酶与质膜的弱锚定及其在红细胞寿命过程中的丢失可能是一种保持细胞唾液酸含量的工具，以避免红细胞的早期老化和毛细血管中细胞聚集的过程。
