Biology subjects

Durante, I. M.

Publications and source records attributed to Durante, I. M..

4 recordsLinked to original sources

bioRxiv2024

Characterization of novel and essential kinetoplast-associated proteins in Trypanosoma brucei

The kinetoplast is one of the defining features of kinetoplastid protists and represents a unique concentration of mitochondrial DNA. This subcellular structure is a highly complex assembly of thousands of mutually catenated, circular DNA molecules as well as up to one hundred dedicated proteins. These components work in tandem to replicate and segregate the mitochondrial genome during cellular division, additionally coordinating with the basal body and flagellum through the tripartite attachment complex (TAC) superstructure. Here, we screened the MitoTag localization repository and identified a number of previously undescribed hypothetical proteins exhibiting putative signals within the kinetoplast of Trypanosoma brucei. Through endogenous tagging we verify their association with the kinetoplast or TAC. The essentiality for several of these kinetoplast proteins (KP) was assessed by RNAi knock-downs, revealing that the newly characterized KP56, KP84 and KP86 are indispensable for growth of the procyclic stage. Additionally, KP37, KP56, and KP84 displayed alterations in the abundance of maxicircles or minicircles, while the depletion of KP84 and KP86 resulted in cell cycle alternations. Pulldown assays using the endogenously V5-tagged cell lines identified novel interactors, which were additionally subjected to endogenous tagging for subcellular localization, revealing two additional proteins (KP45 and KP66) with dual localization to the kinetoplast and throughout the mitochondrial lumen. This work represents the most extensive identification of novel KPs to date and provides a methodological pipeline for the characterization of remaining KPs to further understand this intricate molecular structure.

cell biology↗

bioRxiv2024

A novel nabelschnur protein regulates segregation of the kinetoplast DNA in Trypanosoma brucei

The kinetoplast DNA (kDNA), a distinctive arrangement of mitochondrial DNA found in trypanosomatid protists, comprises a concatenated network of minicircles and maxicircles that undergo division and segregation once during each cell cycle. Despite the identification and characterization of numerous proteins involved in kDNA maintenance and replication, its segregation and the formation of the nabelschnur remain poorly understood on a molecular level. This enigmatic filamentous structure, transiently appearing in Trypanosoma brucei, connects the daughter kDNA networks prior to their complete segregation. Here, we characterize TbNAB70, a high mobility group box-like protein localized exclusively to the nabelschnur and the kDNA disc. Our findings demonstrate that TbNAB70 is critical for the segregation, but not replication, of kDNA, a so far unprecedented phenotype. Furthermore, structural predictions suggest that this protein holds the capacity to bind to kDNA illuminating the exact molecular mechanisms of segregation involved. Thus, we propose that TbNAB70 plays a pivotal role in the faithful and efficient segregation of the daughter kDNA networks.

molecular biology↗

bioRxiv2023

Evolutionary repurposing of trypanosomal Pam18 and Pam16 reveals a new regulatory circuit for mitochondrial genome replication

Protein import and genome replication are essential processes for mitochondrial biogenesis and propagation. The J-domain proteins Pam16 and Pam18 regulate the presequence translocase of the mitochondrial inner membrane. In the protozoan Trypanosoma brucei, their counterparts are TbPam16 and TbPam18, which are essential for the procyclic form of the parasite, though not involved in mitochondrial protein import. Here, we show that during evolution, the two proteins have been repurposed to regulate the replication of maxicircles within the intricate kDNA network, the most complex mitochondrial genome known. TbPam18 and TbPam16 have inactive J-domains suggesting a function independent of heat shock proteins. However, their single transmembrane domain is essential for function. Pulldown of TbPam16 identifies a putative client protein, termed MaRF11, the depletion of which causes the selective loss of maxicircles, akin to the effects observed for TbPam18 and TbPam16. Moreover depletion of the mitochondrial proteasome results in increased levels of MaRF11. Thus, we propose a model for a membrane-bound regulatory circuit that controls maxicircle replication in response to an unknown nuclear signal. This model posits that MaRF11 directly mediates maxicircle replication, that its level is controlled by proteasomal digestion, and that it is protected from degradation by binding to the TbPam18/TbPam16 dimer.

biochemistry↗

bioRxiv2021

Brain-wide neuronal activation and functional connectivity are modulated by prior exposure to repetitive learning episodes.

Memory storage and retrieval are shaped by past experiences. Prior learning and memory episodes have numerous impacts on brain structure from micro to macroscale. Previous experience with specific forms of learning increases the efficiency of future learning. It is less clear whether such practice effects on one type of memory might also have transferable effects to other forms of memory. Different forms of learning and memory rely on different brain-wide networks but there are many points of overlap in these networks. Enhanced structural or functional connectivity caused by one type of learning may be transferable to another type of learning due to overlap in underlying memory networks. Here, we investigated the impact of prior chronic spatial training on the task-specific functional connectivity related to subsequent contextual fear memory recall in mice. Our results show that mice exposed to prior spatial training exhibited decreased brain-wide activation compared to control mice during the retrieval of a context fear memory. With respect to functional connectivity, we observed changes in several network measures notably an increase in global efficiency. Interestingly, we also observed an increase in network resilience based on simulated targeted node deletion. Overall, this study suggests that chronic learning has transferable effects on the functional connectivity networks of other types of learning and memory. The generalized enhancements in network efficiency and resilience suggest that learning itself may protect brain networks against deterioration.

neuroscience↗