Department of Molecular Genetics and Microbiology, Duke University, Durham, North Carolina, USA.
PLoS One. 2012;7(8):e44192. doi: 10.1371/journal.pone.0044192. Epub 2012 Aug 31.
Candida lusitaniae is an emerging fungal pathogen that infects immunocompromised patients including HIV/AIDS, cancer, and neonatal pediatric patients. Though less prevalent than other Candida species, C. lusitaniae is unique in its ability to develop resistance to amphotericin B. We investigated the role of the calcium-activated protein phosphatase calcineurin in several virulence attributes of C. lusitaniae including pseudohyphal growth, serum survival, and growth at 37°C. We found that calcineurin and Crz1, a C. albicans Crz1 homolog acting as a downstream target of calcineurin, are required for C. lusitaniae pseudohyphal growth, a process for which the underlying mechanism remains largely unknown in C. lusitaniae but hyphal growth is fundamental to C. albicans virulence. We demonstrate that calcineurin is required for cell wall integrity, ER stress response, optimal growth in serum, virulence in a murine systemic infection model, and antifungal drug tolerance in C. lusitaniae. To further examine the potential of targeting the calcineurin signaling cascade for antifungal drug development, we examined the activity of a calcineurin inhibitor FK506 in combination with caspofungin against echinocandin resistant C. lusitaniae clinical isolates. Broth microdilution and drug disk diffusion assays demonstrate that FK506 has synergistic fungicidal activity with caspofungin against echinocandin resistant isolates. Our findings reveal that pseudohyphal growth is controlled by the calcineurin signaling cascade, and highlight the potential use of calcineurin inhibitors and caspofungin for emerging drug-resistant C. lusitaniae infections.
卡氏葡萄牙念珠菌是一种新兴的真菌病原体，感染免疫功能低下的患者，包括 HIV/AIDS、癌症和新生儿儿科患者。虽然不如其他念珠菌物种常见，但卡氏葡萄牙念珠菌具有对抗两性霉素 B 产生耐药性的独特能力。我们研究了钙激活蛋白磷酸酶钙调神经磷酸酶在卡氏葡萄牙念珠菌的几种毒力特性中的作用，包括假菌丝生长、血清存活和在 37°C 下的生长。我们发现钙调神经磷酸酶和 Crz1（一种作为钙调神经磷酸酶下游靶标的 C. albicans Crz1 同源物）是卡氏葡萄牙念珠菌假菌丝生长所必需的，这一过程的潜在机制在卡氏葡萄牙念珠菌中仍知之甚少，但菌丝生长是 C. albicans 毒力的基础。我们证明钙调神经磷酸酶是细胞壁完整性、内质网应激反应、血清中最佳生长、小鼠系统性感染模型中的毒力以及卡氏葡萄牙念珠菌抗真菌药物耐受性所必需的。为了进一步研究靶向钙调神经磷酸酶信号级联进行抗真菌药物开发的潜力，我们研究了钙调神经磷酸酶抑制剂 FK506 与卡泊芬净联合治疗棘白菌素耐药的卡氏葡萄牙念珠菌临床分离株的活性。肉汤微量稀释和药敏纸片扩散试验表明，FK506 与卡泊芬净联合对棘白菌素耐药分离株具有协同杀菌活性。我们的研究结果表明，假菌丝生长受钙调神经磷酸酶信号级联的控制，并强调了钙调神经磷酸酶抑制剂和卡泊芬净在治疗新兴耐药性卡氏葡萄牙念珠菌感染方面的潜在用途。
