Deciphering the functional interplay between mitochondrial inner membrane remodelling regulators and mitochondrial RNA granule integrity

• Applicant: Dr. Arun Kumar Kondadi
• Subject Area: Biochemistry ; Cell Biology
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 465350547

Mitochondria are vital double membrane-enclosed cellular organelles playing essential metabolic roles in eukaryotes. The inner membrane (IM) invaginates to form the cristae membrane (CM) and connects to the remaining IM (inner boundary membrane (IBM)) by crista junctions (CJs). CJs are roughly 25 nm slot-like structures which act as a diffusion barrier for proteins between CM and IBM. The MICOS complex enriched at the CJs comprises of seven different proteins. MIC26 and MIC27, which are part of the MICOS complex, belong to the apolipoprotein family. MIC26 and MIC27 are reciprocally regulated at the protein level i.e the levels of MIC26 increase upon depletion of MIC27 and vice versa. While studying the morphology of mitochondrial RNA granules (MRGs) using FASTKD2, we intriguingly found a total loss of FASTKD2 in the MRGs of cells specifically knocked out for both MIC26 and MIC27 (Double Knockouts (DKOs)). We also found MIC26 and MIC27 levels decreased and increased by half respectively in FASTKD2 knockouts (KOs) compared to control cells. Therefore, we would like to study the significance of such an interesting mutual regulation between MICOS apolipoproteins and FASTKD2, an MRG-associated protein. We will determine the possible mechanisms leading to such a mutual regulation. Further, we will decipher the nanoscale organisation of MIC26, MIC27 and FASTKD2 at the IM using STED super-resolution nanoscopy and mobility of the mentioned proteins in FASTKD2 KOs, MIC26 and MIC27 DKOs using FRAP technique. Last but not the least, we will determine the functional significance of the mutual regulation between MIC26, MIC27 present at the CJs on one hand and FASTKD2 associated with the MRGs on the other hand. In conclusion, we will contribute to understanding of a novel mechanism connecting mitochondrial RNA biology and IM remodelling which could plausibly explain the pathophysiology associated with these proteins.

• DFG Programme: Research Grants