Chen Y, Garrison S, Weis J J, Weis J H
Division of Cell Biology and Immunology, Department of Pathology, University of Utah School of Medicine, Salt Lake City, Utah 84132, USA.
J Biol Chem. 1998 Apr 10;273(15):8711-8. doi: 10.1074/jbc.273.15.8711.
We have sought to develop methodologies to identify genes that are preferentially expressed during the differentiation of mast cells from their hematopoietic stem cell precursors. By using a modified differential display protocol, we compared a subset of transcripts expressed in bone marrow cells differentiated into immature mast cells with the exogenous addition of stem cell factor (SCF) or interleukin 3. One gene was identified that was preferentially expressed in the SCF-derived cells and encodes a novel murine integrin beta subunit-like molecule, dubbed Pactolus-1 (Pactolus). Two distinct forms of Pactolus mRNA were detected which, via alternative splicing, are predicted to encode a membrane-bound form and truncated version of the protein. The full-length Pactolus gene product is very similar to a number of beta subunit integrin chains, particularly beta2, with the notable exceptions of the apparent deletion of the metal-binding site within the putative metal ion-dependent adhesion site-like domain of the Pactolus gene product and a cytoplasmic domain that shares no obvious homology to similar domains of the other beta subunit integrin proteins. Although the Pactolus sequence was first identified in immature mast cell samples, screening of murine tissues indicated the highest level of Pactolus expression was found in the bone marrow, suggesting that the expression of Pactolus is confined to immature and maturing bone marrow-derived cells, and that the SCF-derived mast cells are more representative of this state than are the interleukin 3-derived mast cells. Immunoprecipitation of Pactolus revealed a cell-surface protein with an apparent molecular mass of about 95 kDa. Surprisingly, no associating alpha integrin subunit could be identified suggesting that either Pactolus does not associate with another integrin subunit or the association is too weak to be identified. These data suggest that Pactolus represents a gene and gene product related to those of the integrin beta subunits but whose function(s) may be quite distinct from those of the integrin beta subunits.
我们试图开发一些方法来鉴定在肥大细胞从造血干细胞前体分化过程中优先表达的基因。通过使用改良的差异显示方案，我们比较了在添加干细胞因子（SCF）或白细胞介素3的情况下分化为未成熟肥大细胞的骨髓细胞中表达的一部分转录本。鉴定出一个在SCF衍生细胞中优先表达的基因，它编码一种新的小鼠整合素β亚基样分子，命名为帕克托罗斯-1（Pactolus）。检测到两种不同形式的Pactolus mRNA，通过可变剪接，预计它们编码该蛋白的膜结合形式和截短版本。全长Pactolus基因产物与许多β亚基整合素链非常相似，特别是β2，但明显的例外是Pactolus基因产物的假定金属离子依赖性粘附位点样结构域内的金属结合位点明显缺失，以及其胞质结构域与其他β亚基整合素蛋白的类似结构域没有明显的同源性。尽管Pactolus序列最初是在未成熟肥大细胞样本中鉴定出来的，但对小鼠组织的筛选表明，在骨髓中发现Pactolus的表达水平最高，这表明Pactolus的表达局限于未成熟和正在成熟的骨髓衍生细胞，并且SCF衍生的肥大细胞比白细胞介素3衍生的肥大细胞更能代表这种状态。对Pactolus的免疫沉淀显示出一种表观分子量约为95 kDa的细胞表面蛋白。令人惊讶的是，没有鉴定出与之相关的α整合素亚基，这表明要么Pactolus不与另一个整合素亚基结合，要么这种结合太弱而无法鉴定。这些数据表明，Pactolus代表一个与整合素β亚基相关的基因和基因产物，但其功能可能与整合素β亚基的功能有很大不同。
