Glycosylphosphatidylinositol (GPI)-anchored proteins (GPI-APs) are associated with the surface of eucaryotic cells only through a covalently coupled carboxy-terminal GPI glycolipid structure which is anchored at the outer leaflet of plasma membranes. This mode of membrane association may be responsible for the recent observations that full-length GPI-APs harbouring the complete GPI anchor are (i) released from isolated rat adipocytes in vitro and (ii) expressed in rat and human serum. The upregulation of the adipocyte release in response to increased cell size and blood glucose/insulin levels of the donor rats and downregulation of the expression in serum of insulin resistant and diabetic rats have been reconciled with enhanced degradation of the full-length GPI-APs released into micelle-like complexes together with (lyso) phospholipids and cholesterol by serum GPI-specific phospholipase D (GPI-PLD).

Here by using a sensitive and reliable sensing method for full-length GPI-APs, which relies on surface acoustic waves propagating over microfluidic chips, the upregulation of (i) the release of the full-length GPI-APs CD73, alkaline phosphatase and CD55 from isolated adipocyte plasma membranes monitored in a “lab-on-the-chip” configuration, (ii) their release from isolated rat adipocytes into the incubation medium and (iii) the lipolytic cleavage of their GPI anchors in serum was demonstrated to increase with age (3–16 weeks) and body weight (87−477 g) of (healthy) donor rats. In contrast, the amount of full-length GPI-APs in rat serum, as determined by chip-based sensing, turned out to decline with age/body weight. These correlations suggest that age-/weight-induced alterations (in certain biophysical/biochemical characteristics) of plasma membranes are responsible for the release of full-length GPI-APs which becomes counteracted by elevated GPI-PLD activity in serum. Thus, sensitive and specific measurement of these GPI-AP-relevant parameters may be useful for monitoring of age-related cell surface changes, in general, and diseases, in particular.

糖基磷脂酰肌醇 (GPI) 锚定蛋白 (GPI-AP) 仅通过共价偶联的羧基末端 GPI 糖脂结构与真核细胞表面相关联，该结构锚定在质膜的外小叶上。这种膜结合模式可能是最近观察到的具有完整 GPI 锚的全长 GPI-APs 是 (i) 从体外分离的大鼠脂肪细胞中释放的原因(ii) 在大鼠和人血清中表达。响应于供体大鼠的细胞大小和血糖/胰岛素水平的增加，脂肪细胞释放的上调以及胰岛素抵抗和糖尿病大鼠血清中表达的下调与释放的全长 GPI-AP 的降解增强相协调。通过血清 GPI 特异性磷脂酶 D (GPI-PLD) 与（溶血）磷脂和胆固醇一起形成胶束样复合物。

在这里，通过对全长 GPI-APs 使用灵敏可靠的传感方法，该方法依赖于在微流控芯片上传播的表面声波，上调 (i) 全长 GPI-APs CD73、碱性磷酸酶和 CD55 的释放来自在“芯片实验室”配置中监测的分离脂肪细胞质膜，(ii) 它们从分离的大鼠脂肪细胞释放到培养介质中，以及 (iii) 血清中 GPI 锚的脂解裂解被证明随着（健康）供体大鼠的年龄（3-16 周）和体重（87-477 克）。相比之下，通过基于芯片的传感确定的大鼠血清中全长 GPI-AP 的数量，随着年龄/体重的增加而下降。这些相关性表明，年龄/体重引起的质膜改变（在某些生物物理/生化特征中）是全长 GPI-AP 的释放的原因，而血清中 GPI-PLD 活性升高会抵消全长 GPI-AP。因此，对这些 GPI-AP 相关参数的敏感和特异性测量可能有助于监测与年龄相关的细胞表面变化，尤其是疾病。