Dokument: Deciphering the Multifaceted Role of MIC13 in Cristae Formation and Mitochondrial Hepato- Encephalopathy
| Titel: | Deciphering the Multifaceted Role of MIC13 in Cristae Formation and Mitochondrial Hepato- Encephalopathy | |||||||
| URL für Lesezeichen: | https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=66381 | |||||||
| URN (NBN): | urn:nbn:de:hbz:061-20240716-165019-8 | |||||||
| Kollektion: | Dissertationen | |||||||
| Sprache: | Deutsch | |||||||
| Dokumententyp: | Wissenschaftliche Abschlussarbeiten » Dissertation | |||||||
| Medientyp: | Text | |||||||
| Autor: | Naha, Ritam [Autor] | |||||||
| Dateien: |
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| Beitragende: | Prof. Dr. Reichert, Andreas [Gutachter] Prof. Dr. Distelmaier, Felix [Gutachter] | |||||||
| Stichwörter: | Cristae | |||||||
| Dewey Dezimal-Klassifikation: | 500 Naturwissenschaften und Mathematik » 540 Chemie | |||||||
| Beschreibungen: | The Mitochondrial Contact Site and Cristae Organizing System (MICOS) is a key regulator of mitochondrial ultrastructure, consisting of seven core proteins which are divided into two subcomplexes: MIC60-subcomplex including MIC60/MIC19/MIC25 and MIC10-subcomplex including MIC10/MIC26/MIC27, with MIC13 previously known to bridge the two subcomplexes. Mutation in MIC13 induces loss of the MIC10 subcomplex and a mitochondrial ultrastructure abnormality with a dominant pronounced onion-like crista arrangement. Patient mutations in Qil1/MIC13 cause mitochondrial hepato-encephalopathy, a condition with severe hepatic and neurodegenerative implications, leading to early onset lethality. Crucialness of MIC13 for mitochondrial function as well as patient survival underscores the relevance of a detailed study to unravel the underlying molecular mechanism of MIC13 in formation of crista junctions (CJs). It is reported while deficiency in MIC13 triggers a destabilization of the MIC10-subcomplex, leading to pronounced abnormalities in cristae formation, the MIC60-subcomplex remains relatively unaltered in protein levels, yet MIC13 modulates its assembly as indicated by variations in molecular weight migration patterns. Consistent with the conclusion as MIC60 being the master regulator of MICOS complex assembly. Central to MIC13's functionality are the conserved WN and GxxxG motifs- key structural motifs necessary for maintaining the stability of MIC13 and its interaction within the MICOS complex.
In this thesis, I aimed to significantly advance the understanding of MIC13 beyond its presumed structural role. A significant discovery from this thesis describes a regulatory role of MIC13 on the mitochondrial protease YME1L. This rewires the hypothesis of MIC13 being a bridging protein, by revealing its critical function in maintaining the stability of the MIC10-subcomplex by regulating YME1L activity. We demonstrate that depleting YME1L in MIC13 deficient cells effectively restores the MIC10 subcomplex assembly, its interaction with MIC60 and significantly rescues CJs. This marks a fundamental shift in the current understanding of MICOS assembly. Furthermore, elucidating the interactome of MIC13, we identified stomatin- like protein 2 (SLP2) as a novel player in cristae morphogenesis, which extends its functional spectrum beyond the previously identified role of regulating mitochondrial hyperfusion in cellular stress condition. SLP2 emerged as a stabilizer for the MICOS subunit MIC26 via regulating YME1L activity, and depletion resulting in crista swelling and significant loss in CJs. The synergistic interplay between MIC13 and SLP2 is critical for the assembly of the MIC60- subcomplex and subsequently the integration of mitochondrial membrane bridging (MIB) proteins such as SAM50 and MTX1, adding a new layer of understanding of MICOS assembly. The assembly kinetics of MIC60 into the MICOS complex was found to be dependent on SLP2 upon partially assembled MIC10-subcomplex. While MIC13 is essential for MIC10 stability, the presence of SLP2 is instrumental in the assembly kinetics of the MIC60-subcomplex in conjugation with a pre-assembled MIC10-subcomplex, leading to a hypothesis that MIC10- subcomplex and SLP2 provides a ‘seeding’ ground for efficient assembly of MIC60- subcomplex and MIB complex. In conclusion our 'seeder model' posits that the MIC10- subcomplex, together with SLP2, promotes the efficient assembly of the MIC60 subcomplex and MIB complex. Validation of this model is achieved through YME1L knockdown in cells deficient in both MIC13 and SLP2, which leads to the restoration of the MIC10-subcomplex and consequently facilitates a more effective assembly of the MIC60-subcomplex without any conclusive alterations in their steady-state levels, as well as the MIB proteins SAM50 and MTX1. This 'seeder complex' of MIC10 and SLP2 underscores a novel paradigm within the MICOS assembly process, vital for the formation of crista junctions. These insights not only propel our understanding of mitochondrial dynamics but also to the molecular mechanism involved in the development mitochondrial hepato-encephalopathyThe Mitochondrial Contact Site and Cristae Organizing System (MICOS) is a key regulator of mitochondrial ultrastructure, consisting of seven core proteins which are divided into two subcomplexes: MIC60-subcomplex including MIC60/MIC19/MIC25 and MIC10-subcomplex including MIC10/MIC26/MIC27, with MIC13 previously known to bridge the two subcomplexes. Mutation in MIC13 induces loss of the MIC10 subcomplex and a mitochondrial ultrastructure abnormality with a dominant pronounced onion-like crista arrangement. Patient mutations in Qil1/MIC13 cause mitochondrial hepato-encephalopathy, a condition with severe hepatic and neurodegenerative implications, leading to early onset lethality. Crucialness of MIC13 for mitochondrial function as well as patient survival underscores the relevance of a detailed study to unravel the underlying molecular mechanism of MIC13 in formation of crista junctions (CJs). It is reported while deficiency in MIC13 triggers a destabilization of the MIC10-subcomplex, leading to pronounced abnormalities in cristae formation, the MIC60-subcomplex remains relatively unaltered in protein levels, yet MIC13 modulates its assembly as indicated by variations in molecular weight migration patterns. Consistent with the conclusion as MIC60 being the master regulator of MICOS complex assembly. Central to MIC13's functionality are the conserved WN and GxxxG motifs- key structural motifs necessary for maintaining the stability of MIC13 and its interaction within the MICOS complex. In this thesis, I aimed to significantly advance the understanding of MIC13 beyond its presumed structural role. A significant discovery from this thesis describes a regulatory role of MIC13 on the mitochondrial protease YME1L. This rewires the hypothesis of MIC13 being a bridging protein, by revealing its critical function in maintaining the stability of the MIC10-subcomplex by regulating YME1L activity. We demonstrate that depleting YME1L in MIC13 deficient cells effectively restores the MIC10 subcomplex assembly, its interaction with MIC60 and significantly rescues CJs. This marks a fundamental shift in the current understanding of MICOS assembly. Furthermore, elucidating the interactome of MIC13, we identified stomatin- like protein 2 (SLP2) as a novel player in cristae morphogenesis, which extends its functional spectrum beyond the previously identified role of regulating mitochondrial hyperfusion in cellular stress condition. SLP2 emerged as a stabilizer for the MICOS subunit MIC26 via regulating YME1L activity, and depletion resulting in crista swelling and significant loss in CJs. The synergistic interplay between MIC13 and SLP2 is critical for the assembly of the MIC60- subcomplex and subsequently the integration of mitochondrial membrane bridging (MIB) proteins such as SAM50 and MTX1, adding a new layer of understanding of MICOS assembly. The assembly kinetics of MIC60 into the MICOS complex was found to be dependent on SLP2 upon partially assembled MIC10-subcomplex. While MIC13 is essential for MIC10 stability, the presence of SLP2 is instrumental in the assembly kinetics of the MIC60-subcomplex in conjugation with a pre-assembled MIC10-subcomplex, leading to a hypothesis that MIC10- subcomplex and SLP2 provides a ‘seeding’ ground for efficient assembly of MIC60- subcomplex and MIB complex. In conclusion our 'seeder model' posits that the MIC10- subcomplex, together with SLP2, promotes the efficient assembly of the MIC60 subcomplex and MIB complex. Validation of this model is achieved through YME1L knockdown in cells deficient in both MIC13 and SLP2, which leads to the restoration of the MIC10-subcomplex and consequently facilitates a more effective assembly of the MIC60-subcomplex without any conclusive alterations in their steady-state levels, as well as the MIB proteins SAM50 and MTX1. This 'seeder complex' of MIC10 and SLP2 underscores a novel paradigm within the MICOS assembly process, vital for the formation of crista junctions. These insights not only propel our understanding of mitochondrial dynamics but also to the molecular mechanism involved in the development mitochondrial hepato-encephalopathy | |||||||
| Lizenz: |  Dieses Werk ist lizenziert unter einer Creative Commons Namensnennung 4.0 International Lizenz | |||||||
| Fachbereich / Einrichtung: | Mathematisch- Naturwissenschaftliche Fakultät | |||||||
| Dokument erstellt am: | 16.07.2024 | |||||||
| Dateien geändert am: | 16.07.2024 | |||||||
| Promotionsantrag am: | 04.04.2024 | |||||||
| Datum der Promotion: | 24.06.2024 |
