Aiba K, Urushihara H, Yanagisawa K
Institute of Biological Sciences, University of Tsukuba, Ibaraki, Japan.
Differentiation. 1992 Mar;49(2):63-8. doi: 10.1111/j.1432-0436.1992.tb00769.x.
Sexual cell fusion occurs between NC4 and HM1, the heterothallic strains in Dictyostelium discoideum. Cells of these strains are fusion incompetent when cultured on agar plates in the light and become fusion competent upon cultivation in a liquid medium in darkness. Two cell-surface components, gp70 and gp138, have been identified and characterized as being relevant to sexual cell fusion. Both are glycoproteins, and the former is detected only in fusion-competent HM1 cells, while the latter is detected both in fusion-competent HM1 and fusion-competent NC4 cells. We therefore suspect gp 70 to be responsible for cell recognition and gp138, for membrane fusion. Therefore, NC4 cells are expected to possess specific surface molecule(s) that can be recognized by HM1 cells. In the present study, we raised monoclonal antibodies (mAbs) against membrane fractions of NC4 cells and selected fusion-inhibiting mAbs to identify novel molecules related to sexual cell fusion in D. discoideum. Out of the five mAbs we obtained three, DE1, GG6, and HH9, were characterized. DE1 recognized antigens that specifically existed in fusion-competent NC4 cells but not in fusion-incompetent NC4 or HM1 cells. GG6 recognized cell-surface proteins with approximate molecular weights of 125 and 32 kDa in both fusion-competent NC4 and fusion-competent HM1 cells. In addition GG6 also recognised other proteins commonly present in fusion-incompetent cells. The 125 kDa protein appeared to be the same as gp138. The epitope recognized by HH9 was sodium dodecyl sulfate (SDS)-sensitive.(ABSTRACT TRUNCATED AT 250 WORDS)
性细胞融合发生在盘基网柄菌的异宗配合菌株NC4和HM1之间。当这些菌株的细胞在光照条件下于琼脂平板上培养时，它们无融合能力，而在黑暗中于液体培养基中培养时则具备融合能力。已鉴定并表征了两种细胞表面成分gp70和gp138与性细胞融合相关。二者均为糖蛋白，前者仅在具备融合能力的HM1细胞中检测到，而后者在具备融合能力的HM1细胞和具备融合能力的NC4细胞中均能检测到。因此，我们推测gp70负责细胞识别，而gp138负责膜融合。所以，预计NC4细胞拥有能被HM1细胞识别的特定表面分子。在本研究中，我们制备了针对NC4细胞膜组分的单克隆抗体（mAb），并筛选出抑制融合的mAb以鉴定与盘基网柄菌性细胞融合相关的新分子。在我们获得的5种mAb中，对其中3种，即DE1、GG6和HH9进行了表征。DE1识别的抗原特异性存在于具备融合能力的NC4细胞中，而不存在于无融合能力的NC4细胞或HM1细胞中。GG6在具备融合能力的NC4细胞和具备融合能力的HM1细胞中均识别分子量约为125 kDa和32 kDa的细胞表面蛋白。此外，GG6还识别无融合能力细胞中普遍存在的其他蛋白。125 kDa的蛋白似乎与gp138相同。HH9识别的表位对十二烷基硫酸钠（SDS）敏感。（摘要截短于250词）
