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Annual Review of Biochemistry Jun 2017Mitochondria are essential organelles with numerous functions in cellular metabolism and homeostasis. Most of the >1,000 different mitochondrial proteins are synthesized... (Review)
Review
Mitochondria are essential organelles with numerous functions in cellular metabolism and homeostasis. Most of the >1,000 different mitochondrial proteins are synthesized as precursors in the cytosol and are imported into mitochondria by five transport pathways. The protein import machineries of the mitochondrial membranes and aqueous compartments reveal a remarkable variability of mechanisms for protein recognition, translocation, and sorting. The protein translocases do not operate as separate entities but are connected to each other and to machineries with functions in energetics, membrane organization, and quality control. Here, we discuss the versatility and dynamic organization of the mitochondrial protein import machineries. Elucidating the molecular mechanisms of mitochondrial protein translocation is crucial for understanding the integration of protein translocases into a large network that controls organelle biogenesis, function, and dynamics.
Topics: Carrier Proteins; Eukaryotic Cells; Gene Expression; Humans; Isoenzymes; Mitochondria; Mitochondrial Membrane Transport Proteins; Mitochondrial Membranes; Mitochondrial Precursor Protein Import Complex Proteins; Mitochondrial Proteins; Organelle Biogenesis; Protein Conformation, alpha-Helical; Protein Conformation, beta-Strand; Protein Precursors; Protein Transport
PubMed: 28301740
DOI: 10.1146/annurev-biochem-060815-014352 -
International Journal of Molecular... Dec 2022Amyloidoses are a group of diseases associated with deposits of amyloid fibrils in different tissues. So far, 36 different types of amyloidosis are known, each due to... (Review)
Review
Amyloidoses are a group of diseases associated with deposits of amyloid fibrils in different tissues. So far, 36 different types of amyloidosis are known, each due to the misfolding and accumulation of a specific protein. Amyloid deposits can be found in several organs, including the heart, brain, kidneys, and spleen, and can affect single or multiple organs. Generally, amyloid-forming proteins become prone to aggregate due to genetic mutations, acquired environmental factors, excessive concentration, or post-translational modifications. Interestingly, amyloid aggregates are often composed of proteolytic fragments, derived from the degradation of precursor proteins by yet unidentified proteases, which display higher amyloidogenic tendency compared to precursor proteins, thus representing an important mechanism in the onset of amyloid-based diseases. In the present review, we summarize the current knowledge on the proteolytic susceptibility of three of the main human amyloidogenic proteins, i.e., transthyretin, β-amyloid precursor protein, and α-synuclein, in the onset of amyloidosis. We also highlight the role that proteolytic enzymes can play in the crosstalk between intestinal inflammation and amyloid-based diseases.
Topics: Humans; Proteolysis; Amyloidosis; Amyloid; Amyloid beta-Protein Precursor; Protein Precursors; Prealbumin; Peptide Hydrolases
PubMed: 36614141
DOI: 10.3390/ijms24010699 -
The FEBS Journal Jul 2022Coordination of transcription and processing of RNA is a basic principle in regulation of gene expression in eukaryotes. In the case of mRNA, coordination is primarily... (Review)
Review
Coordination of transcription and processing of RNA is a basic principle in regulation of gene expression in eukaryotes. In the case of mRNA, coordination is primarily founded on a co-transcriptional processing mechanism by which a nascent precursor mRNA undergoes maturation via cleavage and modification by the transcription machinery. A similar mechanism controls the biosynthesis of rRNA. However, the coordination of transcription and processing of tRNA, a rather short transcript, remains unknown. Here, we present a model for high molecular weight initiation complexes of human RNA polymerase III that assemble on tRNA genes and process precursor transcripts to mature forms. These multifunctional initiation complexes may support co-transcriptional processing, such as the removal of the 5' leader of precursor tRNA by RNase P. Based on this model, maturation of tRNA is predetermined prior to transcription initiation.
Topics: Humans; RNA Polymerase III; RNA Precursors; RNA Processing, Post-Transcriptional; RNA, Messenger; RNA, Transfer; Ribonuclease P; Transcription, Genetic
PubMed: 33929081
DOI: 10.1111/febs.15904 -
Current Opinion in Cell Biology Apr 2022The majority of cellular proteins are targeted to organelles. Cytosolic ribosomes produce these proteins as precursors with cleavable or non-cleavable targeting... (Review)
Review
The majority of cellular proteins are targeted to organelles. Cytosolic ribosomes produce these proteins as precursors with cleavable or non-cleavable targeting sequences that direct them to receptor proteins on the organelle surface. Multiple targeting factors ensure cellular sorting of the precursor proteins. In co-translational protein import, the ribosome-nascent chain complex is transported to the organellar protein translocase to couple protein synthesis and protein import. In post-translational mode, targeting factors like molecular chaperones guide the precursor proteins from ribosomes to the cell organelle. Defects in protein targeting and import cause mistargeting of proteins to different cellular compartments and challenge the balance of cellular proteostasis. Specific dislocases and degradation machineries remove such mislocalized proteins from the membrane to allow retargeting or their proteasomal turnover. In this review, we discuss targeting and quality control factors that ensure fidelity of protein targeting to mitochondria.
Topics: Mitochondria; Molecular Chaperones; Organelles; Protein Precursors; Protein Transport; Ribosomes
PubMed: 35306313
DOI: 10.1016/j.ceb.2022.02.005 -
The Journal of Investigative Dermatology Jan 2023Deciphering the pathways that regulate human epidermal precursor cell fate is necessary for future developments in skin repair and graft bioengineering. Among them,...
Deciphering the pathways that regulate human epidermal precursor cell fate is necessary for future developments in skin repair and graft bioengineering. Among them, characterization of pathways regulating the keratinocyte (KC) precursor immaturity versus differentiation balance is required for improving the efficiency of KC precursor ex vivo expansion. In this study, we show that the transcription factor MXD4/MAD4 is expressed at a higher level in quiescent KC stem/progenitor cells located in the basal layer of human epidermis than in cycling progenitors. In holoclone KCs, stable short hairpin-RNA‒mediated decreased expression of MXD4/MAD4 increases MYC expression, whose modulation increases the proliferation of KC precursors and maintenance of their clonogenic potential and preserves the functionality of these precursors in three-dimensional epidermis organoid generation. Altogether, these results characterize MXD4/MAD4 as a major piece of the stemness puzzle in the human epidermis KC lineage and pinpoint an original avenue for ex vivo expansion of human KC precursors.
Topics: Humans; Cell Differentiation; Epidermal Cells; Epidermis; Keratinocytes; Basic Helix-Loop-Helix Transcription Factors
PubMed: 36007550
DOI: 10.1016/j.jid.2022.07.020 -
Journal of Applied Behavior Analysis Jul 2019Researchers have developed precursor functional analyses to provide an alternative, and presumably safer, format for functional analysis of severe problem behavior. When... (Review)
Review
Researchers have developed precursor functional analyses to provide an alternative, and presumably safer, format for functional analysis of severe problem behavior. When researchers use functional analysis contingencies for precursor behaviors, it is possible to infer functional characteristics about severe problem behaviors based on patterns of less severe precursor behaviors, permitting practitioners to complete the assessment with less risk to clients, practitioners, or others. The current paper discusses recent advances in the development and validation of precursor identification, and offers suggestions and future directions for investigating and implementing precursor functional analyses. We propose a decision-making model, in which practitioners integrate procedures to identify precursors into the functional-analysis process, to expedite the analysis of severe problem behaviors.
Topics: Humans; Models, Psychological; Problem Behavior; Prodromal Symptoms; Reinforcement, Psychology
PubMed: 31049979
DOI: 10.1002/jaba.571 -
Current Opinion in Biotechnology Jun 2021The widely used polyketide pharmaceuticals in medicine and agriculture are mainly produced by Streptomyces species. These compounds, as secondary metabolites, are not... (Review)
Review
The widely used polyketide pharmaceuticals in medicine and agriculture are mainly produced by Streptomyces species. These compounds, as secondary metabolites, are not involved in essential cellular processes and are usually produced during the stationary phase of fermentation. Consequently, their yields and productivities are often low and frequently limited by the availability of the precursors. The precursor pathways, therefore, are key entities for synthetic biology-driven design and optimization. We discuss recent advances in precursor engineering, in both Streptomyces and other bacteria, focusing on the diverse native and heterologous precursor pathways that could be rewired for polyketide titer improvement. We also highlight the coordination of other required factors to direct the precursors towards polyketide biosynthesis. The precursor-supply enhancement tools and strategies covered in this review will facilitate the design and construction of synthetic Streptomyces 'cell-factories' for efficient polyketide production.
Topics: Pharmaceutical Preparations; Polyketides; Secondary Metabolism; Streptomyces; Synthetic Biology
PubMed: 33316577
DOI: 10.1016/j.copbio.2020.11.006 -
The Biochemical Journal Aug 2021Mitochondria import about 1000 proteins that are produced as precursors on cytosolic ribosomes. Defects in mitochondrial protein import result in the accumulation of... (Review)
Review
Mitochondria import about 1000 proteins that are produced as precursors on cytosolic ribosomes. Defects in mitochondrial protein import result in the accumulation of non-imported precursor proteins and proteotoxic stress. The cell is equipped with different quality control mechanisms to monitor protein transport into mitochondria. First, molecular chaperones guide unfolded proteins to mitochondria and deliver non-imported proteins to proteasomal degradation. Second, quality control factors remove translocation stalled precursor proteins from protein translocases. Third, protein translocases monitor protein sorting to mitochondrial subcompartments. Fourth, AAA proteases of the mitochondrial subcompartments remove mislocalized or unassembled proteins. Finally, impaired efficiency of protein transport is an important sensor for mitochondrial dysfunction and causes the induction of cellular stress responses, which could eventually result in the removal of the defective mitochondria by mitophagy. In this review, we summarize our current understanding of quality control mechanisms that govern mitochondrial protein transport.
Topics: Animals; Humans; Mitochondria; Mitochondrial Membrane Transport Proteins; Mitochondrial Membranes; Mitophagy; Models, Biological; Protein Precursors; Protein Transport; Quality Control
PubMed: 34436539
DOI: 10.1042/BCJ20190584 -
Cancers Oct 2022Carcinomas and precursor lesions of the biliary tract belong to a spectrum of pancreatobiliary neoplasms that share common histology and cell lineages. Over the past two... (Review)
Review
Carcinomas and precursor lesions of the biliary tract belong to a spectrum of pancreatobiliary neoplasms that share common histology and cell lineages. Over the past two decades, preinvasive precursors to biliary tract carcinomas (BTCs) have been identified such as high-grade biliary intraepithelial neoplasm (high-grade BilIN), intraductal papillary neoplasm of bile duct (IPNB) and intracholecystic papillary neoplasm of the gallbladder (ICPN). While a majority of these precursors may arise from the biliary tract mucosa, some originate from the peribiliary glands and Rokitansky-Aschoff sinuses in the walls of the biliary tract. High-grade BilIN is a microscopically identifiable intraepithelial neoplasm of the biliary tract, whereas IPNB and ICPN are grossly visible intraductal or intraluminal preinvasive neoplasms in the bile duct and gallbladder, respectively. These neoplasms show characteristic histologic features according to four cell lineages and two-tiered grading, and show intraepithelial spreading to the surrounding mucosa and involve non-neoplastic glands in the walls of the biliary tract. These precursors are not infrequently associated with stromal invasion, and high-grade BilIN, in particular, are frequently identified in the surrounding mucosa of BTCs. Taken together, it seems likely that progression from these precursors to invasive carcinoma is a major process in biliary carcinogenesis.
PubMed: 36358777
DOI: 10.3390/cancers14215358 -
Frontiers in Endocrinology 2020Maintenance of adipocyte precursors is critical for regulating metabolism and preventing obesity related disease. These precursors have been immortalized and studied in... (Review)
Review
Maintenance of adipocyte precursors is critical for regulating metabolism and preventing obesity related disease. These precursors have been immortalized and studied in cellular models as well as-more recently-in animal models. However, little is known about adipocyte precursors from animals of different ages. Most research has focused on adipocyte precursors during obesity. This review goes over the most recent reports of adipocyte precursors during development and in adulthood. Some of these new analyses are due to new techniques such as single cell-RNA sequencing and temporally controlled lineage tracing. With these tools, we have been able to further our understanding of adipocyte precursor lineages and their different regulatory mechanisms. As we learn more about adipocyte precursor plasticity and regulation, we can hope to use this knowledge for future clinical applications.
Topics: Adipocytes; Adipogenesis; Adipose Tissue; Animals; Cell Differentiation; Humans; Obesity; Single-Cell Analysis
PubMed: 33679601
DOI: 10.3389/fendo.2020.613606