Socolovsky M, Dusanter-Fourt I, Lodish H F
Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142, USA.
J Biol Chem. 1997 May 30;272(22):14009-12. doi: 10.1074/jbc.272.22.14009.
Activation of the erythropoietin receptor is essential for the survival, proliferation, and differentiation of erythroid progenitors. To understand the role of erythropoietin receptor (EpoR) activation in erythroid differentiation, we infected primary erythroid progenitors with high-titer retrovirus encoding the non-hematopoietic prolactin receptor. The infected progenitors responded to prolactin in the absence of Epo by generating fully differentiated erythroid colonies. Therefore, differentiation of erythroid progenitors does not require an intracellular signal generated uniquely by the EpoR; the EpoR does not have an instructive role in erythroid differentiation. We also infected primary erythroid progenitors with retrovirus encoding chimeric receptors containing the extracellular domain of PrlR and the intracellular domain of either the wild-type or truncated EpoRs. A chimeric receptor containing only the membrane-proximal 136 amino acids of the EpoR cytoplasmic domain efficiently supported prolactin-dependent differentiation of erythroid progenitors. Substitution of the single cytoplasmic domain tyrosine in this receptor with phenylalanine (Y343F) eliminated its ability to support differentiation. The minimal EpoR cytoplasmic domain required for erythroid differentiation is therefore the same as that previously reported to be sufficient to support cell proliferation (D'Andrea, A. D., Yoshimura, A., Youssoufian, H., Zon, L. I., Koo, J. W., and Lodish, H. F. (1991) Mol. Cell. Biol. 11, 1980-1987; Miura, O., D'Andrea, A. D., Kabat, D., and Ihle, J. N. (1991) Mol. Cell. Biol. 11, 4895-4902; He, T.-C., Jiang, N., Zhuang, H., Quelle, D. E., and Wojchowski, D. M. (1994) J. Biol. Chem. 269, 18291-18294).
促红细胞生成素受体的激活对于红系祖细胞的存活、增殖和分化至关重要。为了解促红细胞生成素受体（EpoR）激活在红系分化中的作用，我们用编码非造血催乳素受体的高滴度逆转录病毒感染原代红系祖细胞。在没有促红细胞生成素的情况下，被感染的祖细胞对催乳素产生反应，生成完全分化的红系集落。因此，红系祖细胞的分化并不需要由EpoR独特产生的细胞内信号；EpoR在红系分化中不具有指导作用。我们还用编码嵌合受体的逆转录病毒感染原代红系祖细胞，该嵌合受体包含催乳素受体的细胞外结构域和野生型或截短型EpoR的细胞内结构域。仅包含EpoR胞质结构域膜近端136个氨基酸的嵌合受体有效地支持了催乳素依赖的红系祖细胞分化。将该受体中单个胞质结构域酪氨酸替换为苯丙氨酸（Y343F）消除了其支持分化的能力。因此，红系分化所需的最小EpoR胞质结构域与先前报道的足以支持细胞增殖的结构域相同（D'Andrea, A. D., Yoshimura, A., Youssoufian, H., Zon, L. I., Koo, J. W., and Lodish, H. F. (1991) Mol. Cell. Biol. 11, 1980 - 1987; Miura, O., D'Andrea, A. D., Kabat, D., and Ihle, J. N. (1991) Mol. Cell. Biol. 11, 4895 - 4902; He, T.-C., Jiang, N., Zhuang, H., Quelle, D. E., and Wojchowski, D. M. (1994) J. Biol. Chem. 269, 18291 - 18294）。
