Intramembrane proteolytic cleavage by human signal peptide peptidase like 3 and malaria signal peptide peptidase.
Signal peptide peptidase (SPP) is an intramembrane cleaving protease (I-CLiP) identified by its cleavage of several type II membrane signal peptides. To date, only human SPP has been directly shown to have proteolytic activity. Here we demonstrate that the most closely related human homologue of SPP, signal peptide peptidase like 3 (SPPL3), cleaves a SPP substrate, but a more distantly related homologue, signal peptide peptidase like 2b (SPPL2b), does not. These data provide strong evidence that the SPP and SPPL3 have conserved active sites and suggest that the active sites SPPL2b is distinct. We have also synthesized a cDNA designed to express the single SPP gene present in Plasmodium falciparum and cloned this into a mammalian expression vector. When the malaria SPP protein is expressed in mammalian cells it cleaves a SPP substrate. Notably, several human SPP inhibitors block the proteolytic activity of malarial SPP (mSPP). Studies from several model organisms that express multiple SPP homologs demonstrate that the silencing of a single SPP homologue is lethal. Based on these data, we hypothesize that mSPP is a potential a novel therapeutic target for malaria.
Nyborg
Andrew C
AC
Department of Neuroscience, Mayo Clinic Jacksonville, Mayo Clinic College of Medicine, 4500 San Pablo Rd., Jacksonville, Florida 32224, USA.
Ladd
Thomas B
TB
Jansen
Karen
K
Kukar
Thomas
T
Golde
Todd E
TE
D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D016923:Cell Death; D003001:Cloning, Molecular; D017124:Conserved Sequence; D018076:DNA, Complementary; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D016778:Malaria, Falciparum / Q000201:enzymology; D008565:Membrane Proteins / Q000378:metabolism*; D010963:Plasmodium falciparum / Q000201:enzymology* / Q000235:genetics; D015800:Protozoan Proteins / Q000378:metabolism; D014161:Transduction, Genetic
D018076:DNA, Complementary; D004791:Enzyme Inhibitors; D008565:Membrane Proteins; D015800:Protozoan Proteins; D016282:Aspartic Acid Endopeptidases; C460085:signal peptide peptidase; C513914:signal peptide peptidase like 3, human