Targeting and sequestration of truncated Pfs230 in an intraerythrocytic compartment during Plasmodium falciparum gametocytogenesis

Abstract

Summary For malaria to be transmitted, the Plasmodium falciparum parasite must invade an erythrocyte and undergo gametocytogenesis. When mature intraerythrocytic gametocytes are taken up in a blood meal by a mosquito they emerge as gametes and, once fertilized, continue to differentiate into infectious sporozoites. One of the major proteins associated with the surface of the parasite during gamete differentiation is Pfs230, a 360 kDa member of a family of P. falciparum proteins that contains a repeated cysteine motif domain. To characterize the role of different regions of Pfs230, the gene was disrupted by targeted integration and clones isolated that expressed distinct sections of Pfs230. Independent clones D1.356 a and b express the first 452 amino acids (aa) of Pfs230 and do not contain a cysteine motif domain, whereas clones D2.850 a and b express the first 950 aa, including the first cysteine motif domain. Although both sets of clones undergo gametogenesis and produce morphologically normal gametes, neither truncated Pfs230 is located on the surface of the gamete. In clones D1.356 a and b, the 452 aa Pfs230 is secreted into the parasitophorous vacuole and released as a soluble protein when the parasite emerges from the erythrocyte as a gamete. In marked contrast, the 950 aa form of Pfs230 expressed by clones D2.850 a and b is sequestered in a novel tubular compartment in the erythrocyte cytoplasm. This sexual‐stage tubular intraerythrocytic compartment (STIC) is not recognized by antibodies specific for proteins associated with the parasitophorous vacuole membrane (Pfs16 or Exp‐1) or Maurer’s clefts (Pfsbp 1 or mAb LWL1) or intraerythrocytic asexual parasite proteins (PfEMP2 or HRP II).

Distinct Trafficking and Localization of STEVOR Proteins in Three Stages of the Plasmodium falciparum Life Cycle

“…3). We conclude that although MC are present in early gametocytes, STEVOR polypeptides do not localize to MC in gametocytes and are trafficked to the erythrocyte membrane by an MC-independent process, consistent with the findings by Eksi et al (10). Thus, the trafficking and localization of STEVOR is distinct in asexual and sexual parasites.…”

Functional Analysis of the Exported Type IV HSP40 Protein PfGECO in Plasmodium falciparum Gametocytes

“…In gametocyte stages I to V, SBP1 had a discrete punctate pattern that localized both within and at the periphery of the host RBC consistent with previous studies (see Fig. S4 in the supplemental material) (12,32,46,63). This pattern is different from PfGECO's more diffuse staining within the RBC cytoplasm, suggesting that PfGECO does not localize to the Maurer's clefts.…”

“…P. falciparum strain 3D7 was transformed with pDT.Tg23.230-D1.356 (pD1.356) to study the role of gamete surface antigen Pfs230, and two independently transformed, pyrimethamine-resistant lines were obtained as described previously (32). One clonal line produced gametocytes (G ϩ ), whereas the other was gametocyte deficient (G def ).…”

Epidemiology and Infectivity of Plasmodium falciparum and Plasmodium vivax Gametocytes in Relation to Malaria Control and Elimination

“…Pfs230 is synthesized early in gametocyte development, similar to Pfs48/45 (233,499), and is derived from proteolytic cleavage of a 360-kDa precursor molecule into 300-and 35-kDa or 307-and 47-kDa forms (67,369,500). The 300-and 307-kDa membrane-associated Pfs230 fragments that do not contain a GPI anchor remain on the gamete surface (500, 516) as a complex with Pfs48/45 (139,232,233). Pfs230 may be involved in protection of the parasite from the contents of the blood meal, in fertilization (514), or in the formation of exflagellation centers (137).…”