Molecular determinants for subcellular trafficking of the malarial sheddase PfSUB2.

Matthew A. Child,Michael J. Blackman,Sharon Yeoh,Chrislaine Withers‐Martinez,Philippa K. Harris,Christine R. Collins

doi:10.1111/tra.12092

Matthew A. Child, Michael J. Blackman + Show 4 more

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https://doi.org/10.1111/tra.12092

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Abstract

The malaria merozoite invades erythrocytes in the vertebrate host. Iterative rounds of asexual intraerythrocytic replication result in disease. Proteases play pivotal roles in erythrocyte invasion, but little is understood about their mode of action. The Plasmodium falciparum malaria merozoite surface sheddase, PfSUB2, is one such poorly characterized example. We have examined the molecular determinants that underlie the mechanisms by which PfSUB2 is trafficked initially to invasion-associated apical organelles (micronemes) and then across the surface of the free merozoite. We show that authentic promoter activity is important for correct localization of PfSUB2, likely requiring canonical features within the intergenic region 5' of the pfsub2 locus. We further demonstrate that trafficking of PfSUB2 beyond an early compartment in the secretory pathway requires autocatalytic protease activity. Finally, we show that the PfSUB2 transmembrane domain is required for microneme targeting, while the cytoplasmic domain is essential for surface translocation of the protease to the parasite posterior following discharge from micronemes. The interplay of pre- and post-translational regulatory elements that coordinate subcellular trafficking of PfSUB2 provides the parasite with exquisite control over enzyme-substrate interactions.

Highlights

Malaria is a debilitating disease that threatens at least 1 billion people, infects around 500 million and is responsible for approximately 1 million deaths each year [1]
The merozoite attaches to an erythrocyte, as the motor drives the parasite into the cell, components of the parasite surface coat are shed through the action of at least two serine proteases: a rhomboid called ROM4 [5] and the merozoite surface sheddase, a member of the subtilisin-like superfamily called PfSUB2 [6]
The transcriptional profile of pfsub2 closely matches that of pfama1; transcription of both begins at around 43–45 h following erythrocyte invasion and peaks around 48 h post-infection [24,25]

Summary

Introduction

Malaria is a debilitating disease that threatens at least 1 billion people, infects around 500 million and is responsible for approximately 1 million deaths each year [1]. The merozoite attaches to an erythrocyte, as the motor drives the parasite into the cell, components of the parasite surface coat are shed through the action of at least two serine proteases: a rhomboid called ROM4 [5] and the merozoite surface sheddase, a member of the subtilisin-like superfamily called PfSUB2 [6]. Electron microscopic studies of erythrocyte invasion suggested that the enzymes responsible for the proteolysis of surface proteins localize to a region of close association between the parasite and the host cell called the moving junction [7], though a recent study has questioned this supposition [8].

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