PDF(Pubmed)
Abstract：
Mitogen-activated protein kinase (MAPK) pathways are fundamental to the regulation of biological processes in eukaryotic organisms. The basidiomycete Cryptococcus neoformans, known for causing fungal meningitis worldwide, possesses five MAPKs. Among these, Cpk1, Hog1, and Mpk1 have established roles in sexual reproduction, stress responses, and cell wall integrity. However, the roles of Cpk2 and Mpk2 are less understood. Our study elucidates the functional interplay between the Cpk1/Cpk2 and Mpk1/Mpk2 MAPK pathways in C. neoformans. We discovered that CPK2 overexpression compensates for cpk1Δ mating deficiencies via the Mat2 transcription factor, revealing functional redundancy between Cpk1 and Cpk2. We also found that Mpk2 is phosphorylated in response to cell wall stress, a process regulated by the MAPK kinase (MAP2K) Mkk2 and MAP2K kinases (MAP3Ks) Ssk2 and Ste11. Overexpression of MPK2 partially restores cell wall integrity in mpk1Δ by influencing key cell wall components, such as chitin and the polysaccharide capsule. Contrarily, MPK2 overexpression cannot restore thermotolerance and cell membrane integrity in mpk1Δ. These results suggest that Mpk1 and Mpk2 have redundant and opposing roles in the cellular response to cell wall and membrane stresses. Most notably, the dual deletion of MPK1 and MPK2 restores wild-type mating efficiency in cpk1Δ mutants via upregulation of the mating-regulating transcription factors MAT2 and ZNF2, suggesting that the Mpk1 and Mpk2 cooperate to negatively regulate the pheromone-responsive Cpk1 MAPK pathway. Our research collectively underscores a sophisticated regulatory network of cryptococcal MAPK signaling pathways that intricately govern sexual reproduction and cell wall integrity, thereby controlling fungal development and pathogenicity.IMPORTANCEIn the realm of fungal biology, our study on Cryptococcus neoformans offers pivotal insights into the roles of specific proteins called mitogen-activated protein kinases (MAPKs). Here, we discovered the cryptic functions of Cpk2 and Mpk2, two MAPKs previously overshadowed by their dominant counterparts Cpk1 and Mpk1, respectively. Our findings reveal that these \"underdog\" proteins are not just backup players; they play crucial roles in vital processes like mating and cell wall maintenance in C. neoformans. Their ability to step in and compensate when their dominant counterparts are absent showcases the adaptability of C. neoformans. This newfound understanding not only enriches our knowledge of fungal MAPK mechanisms but also underscores the intricate balance and interplay of proteins in ensuring the organism\'s survival and adaptability.
摘要：
丝裂原活化蛋白激酶(MAPK)通路是真核生物生物过程调控的基础。新型担子菌隐球菌，以引起全球真菌性脑膜炎而闻名，拥有五个MAPK。其中,Cpk1，Hog1和Mpk1在有性生殖中已经确立了作用，应激反应，和细胞壁完整性。然而,对Cpk2和Mpk2的作用了解较少。我们的研究阐明了Cpk1/Cpk2和Mpk1/Mpk2MAPK途径之间的功能相互作用。我们发现CPK2过表达通过Mat2转录因子补偿cpk1Δ交配缺陷，揭示Cpk1和Cpk2之间的功能冗余。我们还发现，Mpk2响应细胞壁应激而磷酸化，由MAPK激酶（MAP2K）Mkk2和MAP2K激酶（MAP3K）Ssk2和Ste11调节的过程。MPK2的过表达通过影响关键细胞壁成分部分恢复了mpk1Δ中的细胞壁完整性，如几丁质和多糖胶囊。相反，MPK2过表达不能恢复MPK1Δ的耐热性和细胞膜完整性。这些结果表明，Mpk1和Mpk2在细胞对细胞壁和膜应力的反应中具有冗余和相反的作用。最值得注意的是,MPK1和MPK2的双重缺失通过上调交配调节转录因子MAT2和ZNF2，恢复了cpk1Δ突变体的野生型交配效率，表明Mpk1和Mpk2合作负调节信息素反应性Cpk1MAPK途径。我们的研究共同强调了复杂的隐球菌MAPK信号通路的调节网络，这些信号通路错综复杂地控制有性生殖和细胞壁完整性。从而控制真菌的发育和致病性。在真菌生物学领域的重要性，我们对新生隐球菌的研究提供了对称为丝裂原活化蛋白激酶(MAPKs)的特定蛋白质作用的关键见解.这里,我们发现了Cpk2和Mpk2的神秘功能，这两个MAPK以前分别被其主要对应物Cpk1和Mpk1所掩盖。我们的发现表明，这些“弱者”蛋白质不仅仅是备用者；它们在新生梭菌的交配和细胞壁维持等重要过程中起着至关重要的作用。当他们的优势对应物不存在时，他们介入和补偿的能力展示了新型梭菌的适应性。这种新发现的理解不仅丰富了我们对真菌MAPK机制的认识，而且强调了蛋白质在确保生物体生存和适应性方面的复杂平衡和相互作用。
