Investigation of OPA1 in Mitochondrial Dynamics and Ultrastructure

by Christiaan Stuut
Doctoral thesis
Date of Examination:2024-01-26
Date of issue:2024-03-21
Advisor:Prof. Dr. Stefan Jakobs
Referee:Prof. Dr. Stefan Jakobs
Referee:Prof. Dr. Ricarda Richter-Dennerlein
Persistent Address: http://dx.doi.org/10.53846/goediss-10396

 

 

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Abstract

English

Mitochondria are highly dynamic organelles with a complex ultrastructure. The mitochondrial inner membrane (MIM) is folded into cristae in which oxidative phosphorylation, a process to generate energy for the cell, takes place. Cristae are connected to the flat part of the inner membrane space by crista junctions (CJs). The size and shape of cristae and their junctions is tightly regulated by MICOS, F1Fo ATP synthase, and the dynamin-like GTPase OPA1. The eight isoforms of OPA1 can be proteolytically cleaved by OMA1 and YME1L to create a large number of different OPA1 fragments, that are either membrane bound to the MIM or are soluble in the intermembrane space. The exact localisation of OPA1, as well as its interactions with MICOS proteins, remains unknown. In this work, I analysed the localisation of OPA1 using multiple super-resolution microscopy techniques. I found that OPA1, similarly to MIC60, displays a coordinated clustered distribution along mitochondria, possibly localising to CJs. In human cells deficient of OPA1, I analysed the effect of OPA1-deficiency on CJs using electron tomography. Cells deficient of OPA1 contained slit-like CJs, that were on average over 120 nm in length. By overexpressing MIC10 in these cells, I showed that OPA1 but not MIC10 influences the length of CJs.
Keywords: super-resolution microscopy; STED microscopy; mitochondrial dynamics; OPA1; mitochondria