LIFE CYCLE REGULATION OF PNEUMOCYSTIS CARINII BY MAPK

卡氏肺孢子虫是一种机会性真菌病原体，可引起 免疫系统受损患者的严重肺炎， 尤其是艾滋病患者。卡氏肺吸虫的生活史为 人们对此知之甚少。在密切相关的真菌中，与一种 调控周期蛋白通过G1限制调控基因的转换 在与P.carinii同源的真菌中，细胞周期中的1-7点开始， 信息素交配因子通过有丝分裂原激活抑制启动 蛋白激酶(MAPK)信号转导级联导致细胞 细胞周期停滞和细胞分化。8-14 MAPK磷酸化一个 Cdc2-Cyclin复合体的抑制剂。15-18MAPK是必不可少的 信息素交配级联中控制转换的分子 从有丝分裂生长到接合途径，细胞 分化和增殖。8作为一种基本分子 MAPK调节生物体的生命周期，受一种激酶的调节 通过两个保守的苏氨酸上的磷酸化而激活 和酪氨酸氨基酸。19-24卡氏肺孢子虫与肺泡的附着性 上皮细胞是卡氏肺孢子虫肺炎的一个主要特征，并与 上皮是生物体增殖所必需的。25-26我们的 初步研究表明，卡氏肺孢子虫具有一种MAPK，它是 与参与配对的真菌MAPK高度同源。27因此， 假设MAPK信号转导级联具有中心作用 对卡氏肺孢子虫生活史的调控。我们进一步建议 卡氏肺孢子虫MAPK调节细胞分化和增殖 卡氏肺孢子虫的生物体。为了评估这些假设，我们将 同时进行几项调查。我们将对P. Carinii MAPK基因参与生命周期调控。我们将决定 卡氏肺孢子虫的激酶活性及其调节的磷酸化 MAPK。此外，我们将确定该表达和活性是否 在整个生命周期中受到不同的调节 通过评估分离的包囊和滋养体中的MAPK来检测卡氏肺孢子虫。 最后，我们将确定MAPK在从 通过评估P。 Carinii MAPK与肺泡上皮附着前后及 通过在不同的生活史形式中过量表达MAPK基因。 卡里尼。通过这些调查，我们希望获得重要的 对卡氏肺孢子虫生活史调控的洞察。

Pneumocystis carinii is an opportunistic fungal pathogen which causes severe pneumonia in patients with an impaired immune system, particularly in patients with AIDS. The life cycle of P. carinii is poorly understood. In closely related fungi, Cdc2 associated with a regulatory cyclin controls the transition through the G1 restriction point START in the cell cycle.1-7 In fungi homologous to P. carinii, pheromone mating factors inhibit START through a mitogen-activated protein kinase (MAPK) signal transduction cascade which results in cell cycle arrest and cellular differentiation.8-14 MAPK phosphorylates an inhibitor of the Cdc2-cyclin complex.15-18 MAPK is the essential molecule in the pheromone mating cascade which controls the transition from mitotic growth to a pathway of conjugation, cellular differentiation, and proliferation.8 As an essential molecule regulating an organism's life cycle, MAPK is regulated by a kinase cascade and is activated by phosphorylation on two conserved threonine and tyrosine amino acids.19-24 Attachment of P. carinii to the alveolar epithelium is a central feature of P. carinii pneumonia, and binding to the epithelium is required for the organisms to proliferate.25-26 Our initial studies indicate that P. carinii possesses a MAPK which is highly homologous to fungal MAPK's involved in mating.27 We, therefore, hypothesize that the MAPK signal transduction cascade has a central role in the regulation of the P. carinii life cycle. We further propose that the P. carinii MAPK regulates cellular differentiation and proliferation of P. carinii organisms. To evaluate these hypotheses, we will undertake several parallel investigations. We will characterize the P. carinii MAPK genes involved in life cycle regulation. We will determine the kinase activity and the regulatory phosphorylations for P. carinii MAPK. Further, we will determine whether the expression and activity of P. carinii MAPK is differentially regulated throughout the life cycle of P. carinii by evaluating MAPK in separated cysts and trophozoites. Finally, we will determine the role of MAPK in the transition from one life form to another by evaluating the expression and activity of P. carinii MAPK before and after attachment to the alveolar epithelium and by overexpressing MAPK genes in separated life cycle forms of P. carinii. Through these investigations, we hope to gain important insights into the life cycle regulation of P. carinii.