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Global Parasitology Seminars

Parasitology Seminar Series

Gustavo Arrizabalaga, Ph.D. "The shape-shifting mitochondrion of Toxoplasma gondii"


Title: "The shape-shifting mitochondrion of Toxoplasma gondii"

Speaker:Gustavo Arrizabalaga PhD

Gustavo Arrizabalaga, PhD
Departments of Pharmacology and Toxicology and
Microbiology and Immunology,

Indiana University School of Medicine

Indianapolis, IN


A unique feature of apicomplexan parasites such as Toxoplasma gondii is the presence of a single tubular mitochondrion, which is essential for parasite survival and a validated
drug target. Toxoplasma’s mitochondrion is very dynamic and undergoes morphological
changes throughout the parasite’s life cycle. During parasite division, the mitochondrion
elongates, enters the daughter cells just prior to cytokinesis and undergoes fission.
Extensive morphological changes also occur as the parasite transitions from the
intracellular to the extracellular environment. While inside a host cell the mitochondrion
is maintained in a lasso shape that stretches around the parasite periphery where it has
regions of contact with the parasite pellicle. Promptly after exit from the host cell, these
contact sites disappear, and the mitochondrion collapses Neither the functional
significance nor the proteins involved have been known for the contact between
Toxoplasma’s mitochondrion and pellicle. Recently we have shown that the
mitochondrion’s tethering to the parasite’s membrane system is mediated by a protein
named Lasso Maintenance Factor 1 (LMF1). We have shown that LMF1 interacts with
IMC10, a protein present at the parasite’s inner membrane complex (IMC), mediating a
unique contact site between the IMC and the mitochondrion. Interestingly, parasites
lacking LMF1 or IMC10 do not only fail to tether the mitochondrion and IMC, but also
show defects in organellar distribution during cell division. Consistent with this role, we
observe colocalization of these two proteins early on in mitochondrial inheritance. As
little is known about mitochondrial inheritance, we have used the LMF1/IMC10
interaction as an entry point to dissect the machinery behind mitochondrial division and
inheritance in this parasite. Currently, the Arrizabalaga lab is characterizing the motor
protein involved in mitochondrial inheritance as well as on the identification of other
proteins involved in mitochondrion morphodynamic


Dr. Gustavo Arrizabalaga has been studying the cell biology of the pathogenic parasite Toxoplasma gondii for over 20 years. He received his Ph.D. in Biology from MIT
under the mentorship of Dr. Ruth Lehmann. His doctoral work focused on developmental
biology and translational regulation using Drosophila as a model system. Dr. Arrizabalaga did a post-doctoral fellowship with Dr. John Boothroyd at Stanford University School of Medicine, where he began focusing on how Toxoplasma gondii exits its host cell. In 2012, he joined the Departments of Pharmacology and Toxicology and Microbiology and Immunology at the Indiana University School of Medicine, where he is currently a Professor and an Assistant Dean for Faculty Affairs and Professional Development.

Date: Monday, December 11th, 2023
Time: 12 pm

LocationHill Pavilion Room 132 and available virtually Via Zoom

Questions? Please contact Michael Black if you have questions.

Date and Time


Michael Black