INVESTIGADORES
PARUSSINI GIMENEZ Silvana Fabiola
artículos
Título:
Intramembrane proteolysis of Toxoplasma apical membrane antigen 1 facilitates host-cell invasion but is dispensable for replication
Autor/es:
FABIOLA PARUSSINI; QING TANG; SYED M. MOIN; JEFFREY MITAL; SINISA URBAN; GARY E. WARD
Revista:
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Editorial:
NATL ACAD SCIENCES
Referencias:
Lugar: Washington DC, USA; Año: 2012 vol. 109 p. 7463 - 7468
ISSN:
0027-8424
Resumen:
Apical membrane antigen 1 (AMA1) is a conserved transmembrane adhesin of apicomplexan parasites that plays an important role
in host-cell invasion. Toxoplasma gondii
AMA1 (TgAMA1) is secreted onto the parasite surface and subsequently
released by proteolytic cleavage within its transmembrane
domain. To elucidate the function of
TgAMA1 intramembrane proteolysis, we used a heterologous cleavage assay
to characterize
the determinants within the TgAMA1
transmembrane domain (ALIAGLAVGGVLLLALLGGGCYFA) that govern its processing. Quantitative analysis revealed that the TgAMA1L/G mutation enhanced cleavage by 13-fold compared with wild type. In contrast, the TgAMA1AG/FF mutation reduced cleavage by 30-fold, whereas the TgAMA1GG/FF
mutation had a minor effect on proteolysis; mutating both motifs in a
quadruple mutant blocked cleavage completely. We then
complemented a TgAMA1 conditional knockout
parasite line with plasmids expressing these TgAMA1 variants. Contrary
to expectation,
variants that increased or decreased
TgAMA1 processing by >10-fold had no phenotypic consequences,
revealing that the levels
of rhomboid proteolysis in parasites are
not delicately balanced. Only parasites transgenically expressing or
carrying a true
knock-in allele of the uncleavable TgAMA1AG/FF+GG/FF
mutant showed a growth defect, which resulted from inhibiting invasion
without perturbing intracellular replication. These
data demonstrate that TgAMA1 cleavage
plays a role in invasion, but refute a recently proposed model in which
parasite replication
within the host cell is regulated by
intramembrane proteolysis of TgAMA1.