Systematic Genetic Analysis of the Plasmodium falciparum MSP7-Like Family Reveals Differences in Protein Expression, Location, and Importance in Asexual Growth of the Blood-Stage Parasite
Systematic Genetic Analysis of the Plasmodium falciparum MSP7-Like Family Reveals Differences in Protein Expression, Location, and Importance in Asexual Growth of the Blood-Stage Parasite
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DOI：
10.1128/ec.00048-10
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发表时间：
2010-07-01
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影响因子：
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通讯作者：
Holder, Anthony A.
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作者：
Kadekoppala, Madhusudan;Ogun, Solabomi A.;Holder, Anthony A.
位于恶性疟原虫裂殖子（疟原虫的无性血液阶段的侵入形式）上的蛋白质在疫苗研究中具有相当大的兴趣。裂殖子表面蛋白7（MSP 7）与MSP 1形成复合物，并且由位于染色体13上的多基因家族的成员编码。该家族编码MSP 7和五种MSP 7相关蛋白（MSRP）。在本研究中，我们研究了msrp基因缺失在无性血液阶段的表达及其影响。除了msp 7之外，msrp 2、msrp 3和msrp 5也被转录，并且mRNA很容易通过杂交分析检测到，而msrp 1和msrp 4的mRNA只能通过逆转录（RT）-PCR检测到。尽管有转录的证据，重组MSRP的抗体未能检测到特定的蛋白质，除了MSRP 2的抗体。MSRP 2的连续蛋白水解裂解产生28-和25-kDa形式。然而，裂殖子中不存在MSRP 2; 25-kDa MSRP 2蛋白（MSRP 2（25））是可溶的并且在裂殖子排出时分泌。在3D 7系中通过靶向破坏来删除msrp基因，导致全长转录物的消除。MSRP缺失突变体没有可检测的表型，生长和入侵特性与亲本寄生虫相当;只有MSP 7的缺失导致可检测的生长表型。因此，在这个家族中，一些基因在无性血液阶段以显著水平转录，但相应的蛋白质可能是或可能不是可检测的。表达的蛋白质与裂殖子的相互作用也不同。这些结果突出了基因家族内蛋白质表达水平的意外差异的可能性。
Proteins located on Plasmodium falciparum merozoites, the invasive form of the parasite's asexual blood stage, are of considerable interest in vaccine research. Merozoite surface protein 7 (MSP7) forms a complex with MSP1 and is encoded by a member of a multigene family located on chromosome 13. The family codes for MSP7 and five MSP7-related proteins (MSRPs). In the present study, we have investigated the expression and the effect of msrp gene deletion at the asexual blood stage. In addition to msp7, msrp2, msrp3, and msrp5 are transcribed, and mRNA was easily detected by hybridization analysis, whereas mRNA for msrp1 and msrp4 could be detected only by reverse transcription (RT)-PCR. Notwithstanding evidence of transcription, antibodies to recombinant MSRPs failed to detect specific proteins, except for antibodies to MSRP2. Sequential proteolytic cleavages of MSRP2 resulted in 28- and 25-kDa forms. However, MSRP2 was absent from merozoites; the 25-kDa MSRP2 protein (MSRP2(25)) was soluble and secreted upon merozoite egress. The msrp genes were deleted by targeted disruption in the 3D7 line, leading to ablation of full-length transcripts. MSRP deletion mutants had no detectable phenotype, with growth and invasion characteristics comparable to those of the parental parasite; only the deletion of MSP7 led to a detectable growth phenotype. Thus, within this family some of the genes are transcribed at a significant level in asexual blood stages, but the corresponding proteins may or may not be detectable. Interactions of the expressed proteins with the merozoite also differ. These results highlight the potential for unexpected differences of protein expression levels within gene families.