Mitochondrial Biogenesis in Health and Disease

Project Summary
Mitochondria allow our cells to use oxidative phosphorylation (OXPHOS) as a highly efficient way to generate
ATP. The inner membrane-embedded OXPHOS system enzymes are multimeric complexes composed of
proteins from two different genetic origins, namely the nuclear and the mitochondrial DNA. Nucleus-encoded
proteins are synthesized in cytoplasmic ribosomes and imported into mitochondria. The mitochondrion-
encoded proteins, usually catalytic core subunits of the complexes, are synthesized into distinct mitochondrial
ribosomes. Mutations affecting these processes lead to mitochondrial cardio- and encephalo-myopathies and
have been linked to neurodegeneration, metabolic disease, cancer, and aging.
We have developed a scientific research program aiming to understand the molecular mechanisms
underlying the assembly of mitochondrial complexes of dual genetic origin. Our program includes in-depth
studies into the assembly of three sets of macromolecular structures. (i) Assembly of individual OXPHOs
enzymes, with an emphasis on the assembly of MRC complex IV or cytochrome c oxidase (COX), the terminal
MRC enzyme. (ii) Assembly of MRC enzymes into supramolecular structures known as supercomplexes and
respirasomes. (iii) Assembly and function of the mitoribosome.
In each case, we will pursue three general goals: (i) Define the assembly pathway/s and the order of
incorporation of components and prosthetic groups; (ii) Identify and characterize the assembly factors
involved, and (iii) Disclose regulatory assembly checkpoints, which detect damaged or abnormally folded
components, or coordinate synthesis or maturation of one component with its assembly into the complex.
Studies outlined in this proposal will involve yeast genetics, gene disruption in human cells using gene-editing
strategies, cryo-EM reconstruction of protein complexes and assembly intermediates, and mechanistic
biochemistry in yeast, human cell lines, isolated mitochondria and purified native and recombinant proteins to
gain insight into the role/s of OXPHOS complex, supercomplex and mitoribosome assembly factors. The
analysis of the principles of the biogenesis process and the activities of the assembly factors is of central
importance for our understanding of the molecular basis of human mitochondrial disorders.
Uncovering the mechanisms through which assembly of cellular macrostructures takes place in
standard conditions and under stress remains one of the grand challenges of modern science from a biological
and a biomedical perspective. We anticipate that our program will continue contributing to close the gap in our
understanding of mitochondrial biogenesis in health and disease.

Grant Number: 5R35GM118141-10
NIH Institute/Center: NIH
Principal Investigator: Antoni Barrientos