Periodic Reporting for period 3 - OnTarget (Deciphering the principles governing robust targeting of proteins to organelles)
Reporting period: 2023-09-01 to 2025-02-28
Membrane-enclosed organelles are the hallmark of eukaryotic cellular organization. They enable the compartmentalization of cellular reactions crucial for multicellularity. However they also pose constraints on the cell since proteins, the executors of all cellular functions, that are made in the cytosol, must make it into their respective organelles to function. 50% of eukaryotic proteins are synthesized on cytosolic ribosomes and are then targeted to their respective organelles to properly function. Hence a complete understanding of how proteins get to their functional localization is an important aspect of Cell Biology.
My lab uses the budding yeast Saccharomyces cerevisiae to explore the machinery required for protein targeting to organelles. We are also dedicated to creating and optimizing sophisticated genetic tools to enable us, and others, the use of systematic approaches for probing cell biology. Our ERC project, OnTarget, aimed to uncover new targeting pathways, the proteins that they cater for and new modes of regulation on these pathways.
Since all diseases that are not pathogen borne are due to failures of cellular function - including Cancer, neurodegeneration, diabetes and all 8000 rare diseases - our deep understanding of cellular functions is crucial for uncovering ways to track, diagnose and possible modulate disease.
My lab uses the budding yeast Saccharomyces cerevisiae to explore the machinery required for protein targeting to organelles. We are also dedicated to creating and optimizing sophisticated genetic tools to enable us, and others, the use of systematic approaches for probing cell biology. Our ERC project, OnTarget, aimed to uncover new targeting pathways, the proteins that they cater for and new modes of regulation on these pathways.
Since all diseases that are not pathogen borne are due to failures of cellular function - including Cancer, neurodegeneration, diabetes and all 8000 rare diseases - our deep understanding of cellular functions is crucial for uncovering ways to track, diagnose and possible modulate disease.
In the past year and a half, and thanks to ERC funding, we have made several paradigmatic discoveries in this field:
- We could show that many mitochondrial matrix proteins do not contain a canonical targeting signal yet insert into mitochondria using the same pathways (Bykov et al, EMBO J. 2021)
- We demonstrated that co-translational translocation of membrane proteins occurs in peroxisomes (Dahan et al, Science Advances, 2022)
- We mapped the substrate range for the EMC translocon to the Endoplasmic Reticulum (ER) (Fenech et al, MSB 2022)
- We uncovered a new way for the signal-less matrix protein, Pls1, to enter peroxisomes and its function in the organelle (David et al, 2022)
- We deciphered the function of the Sbh1 subunit of the ER translocon (Barbieri et al, JBC 2023)
- We identified the substrate range of the Sec61 Homologous Translocon (SSH1) and deduced the exact signals enabling its specificity (Cohen et al, EMBO J., 2023)
- We found new targeting information in the peroxisomal membrane transporter, Pxa1 - mutations in whose homolog in humans causes a severe peroxisomal disease (Jansen et al, BBA MCR, 2023)
- We discovered the exact determinants of the targeting factor, Pex9, that make it specific to only a subset of proteins from the general targeting factor Pex5 (Yifrach et al, Biological Chemistry, 2023)
- We understood a new mode of regulation for the targeting factor Pex5 into peroxisomes through phosphorylation (Fischer et al, Biological Chemistry, 2022)
- We defined new ways for peroxisomal matrix proteins to targeting into the organelle in the absence of conventional targeting signals (Yifrach et al, MSB, 2022).
Overall we have made huge strides in understanding how cells maintain a robust, regulated and rapid system for protein sorting
- We could show that many mitochondrial matrix proteins do not contain a canonical targeting signal yet insert into mitochondria using the same pathways (Bykov et al, EMBO J. 2021)
- We demonstrated that co-translational translocation of membrane proteins occurs in peroxisomes (Dahan et al, Science Advances, 2022)
- We mapped the substrate range for the EMC translocon to the Endoplasmic Reticulum (ER) (Fenech et al, MSB 2022)
- We uncovered a new way for the signal-less matrix protein, Pls1, to enter peroxisomes and its function in the organelle (David et al, 2022)
- We deciphered the function of the Sbh1 subunit of the ER translocon (Barbieri et al, JBC 2023)
- We identified the substrate range of the Sec61 Homologous Translocon (SSH1) and deduced the exact signals enabling its specificity (Cohen et al, EMBO J., 2023)
- We found new targeting information in the peroxisomal membrane transporter, Pxa1 - mutations in whose homolog in humans causes a severe peroxisomal disease (Jansen et al, BBA MCR, 2023)
- We discovered the exact determinants of the targeting factor, Pex9, that make it specific to only a subset of proteins from the general targeting factor Pex5 (Yifrach et al, Biological Chemistry, 2023)
- We understood a new mode of regulation for the targeting factor Pex5 into peroxisomes through phosphorylation (Fischer et al, Biological Chemistry, 2022)
- We defined new ways for peroxisomal matrix proteins to targeting into the organelle in the absence of conventional targeting signals (Yifrach et al, MSB, 2022).
Overall we have made huge strides in understanding how cells maintain a robust, regulated and rapid system for protein sorting
We are continuing to work on how proteins make it to their correct cellular local and are focusing on new types of proteins whose targeting pathways have not been discovered - these include:
1. Endoplasmic reticulum (ER) surface proteins
2. ER proteins with signal peptides of low hydrophobicity,
3. Peroxisomal proteins that reach the lumen (matrix) of the organelle yet not targeting signals have been uncovered for them
4. Peroxisomal surface proteins
5. Mitochondrial matrix proteins with no targeting information available
1. Endoplasmic reticulum (ER) surface proteins
2. ER proteins with signal peptides of low hydrophobicity,
3. Peroxisomal proteins that reach the lumen (matrix) of the organelle yet not targeting signals have been uncovered for them
4. Peroxisomal surface proteins
5. Mitochondrial matrix proteins with no targeting information available