Mphande Fingani A, Ribacke Ulf, Kaneko Osamu, Kironde Fred, Winter Gerhard, Wahlgren Mats
Department of Microbiology, Tumor and Cell Biology (MTC) Karolinska Institutet and Swedish Institute for Infectious Disease Control, Nobel's väg 16, Box 280, SE-171 77, Stockholm, Sweden.
Malar J. 2008 Jul 1;7:116. doi: 10.1186/1475-2875-7-116.
In its effort to survive the human immune system, Plasmodium falciparum uses several parasite-derived antigens most of which are expressed at the surface of the parasitized red blood cells (pRBCs). Recently SURFINs, a new family of antigens encoded by the surf multi-gene family, has been reported. One member of the family, SURFIN4.2, was found present both at the pRBC-surface and at the merozoite apex.
The presence of a second SURFIN member, SURFIN4.1 (PFD0100c, PFD0105c) is reported here. Bioinformatic tools were used to study the structure of the surf4.1 gene. To investigate the expression of surf genes PCR and real-time quantitative PCR (Rt-QPCR) were employed and Northern and Western blots were used to confirm the size of the surf4.1 gene and the SURFIN4.1 protein respectively. Localization of SURFIN4.1 was determined using immunofluorescence assays.
The surf4.1 gene was found present in one copy by Rt-QPCR in some parasites (3D7AH1, 3D7S8, 7G8) whereas six copies of the gene were identified in FCR3 and FCR3S1.2. surf4.1 was found transcribed in the late asexual stages of the parasite beginning approximately 32 hours post invasion and throughout the schizont stages with the level of transcription peaking at late schizogony. The levels of transcript correlated with the number of gene copies in FCR3 and 3D7S8. surf4.1 was found to encode a polypeptide of approximately Mw 258 kDa (SURFIN4.1) present within the parasitophorous vacuole (PV), around free merozoites as merozoite-associated material, but not at the pRBC-surface. Despite multiple surf4.1 gene copies in some parasites this was not reflected in the levels of SURFIN4.1 polypeptide.
SURFIN4.1 is a member of the SURFINs, present in the PV and on the released merozoite. The results suggest different SURFINs to be expressed at different locations in the parasite and at distinct time-points during the intra-erythrocytic cycle.
为了在人类免疫系统中存活，恶性疟原虫利用多种寄生虫衍生抗原，其中大多数在被寄生的红细胞（pRBCs）表面表达。最近，有报道称SURFINs是由surf多基因家族编码的一个新的抗原家族。该家族的一个成员SURFIN4.2，被发现既存在于pRBC表面，也存在于裂殖子顶端。
本文报道了另一个SURFIN成员SURFIN4.1（PFD0100c、PFD0105c）的存在。使用生物信息学工具研究surf4.1基因的结构。为了研究surf基因的表达，采用了PCR和实时定量PCR（Rt-QPCR），并分别使用Northern和Western印迹来确认surf4.1基因的大小和SURFIN4.1蛋白的大小。使用免疫荧光测定法确定SURFIN4.1的定位。
通过Rt-QPCR发现，在一些寄生虫（3D7AH1、3D7S8、7G8）中surf4.1基因以单拷贝形式存在，而在FCR3和FCR3S1.2中鉴定出该基因有六个拷贝。发现surf4.1在寄生虫无性发育后期开始转录，大约在入侵后32小时开始，并在整个裂殖体阶段持续转录，转录水平在裂殖后期达到峰值。转录水平与FCR3和3D7S8中的基因拷贝数相关。发现surf4.1编码一种分子量约为258 kDa的多肽（SURFIN4.1），存在于寄生泡（PV）内，作为裂殖子相关物质存在于游离裂殖子周围，但不存在于pRBC表面。尽管在一些寄生虫中有多个surf4.1基因拷贝，但这并未反映在SURFIN4.1多肽的水平上。
SURFIN4.1是SURFINs家族的成员，存在于PV和释放的裂殖子上。结果表明不同的SURFINs在寄生虫的不同位置以及红细胞内周期的不同时间点表达。
