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  • Laboratory of Protein Metabolism in Development and Aging: Pokrzywa Laboratory

Laboratory of Protein Metabolism in Development and Aging: Pokrzywa Laboratory

Wojciech Pokrzywa, PhD 

Correspondence address:
Laboratory of Protein Metabolism in Development and Aging
International Institute of Molecular and Cell Biology
4 Ks. Trojdena Street, 02-109 Warsaw, Poland
Email: This email address is being protected from spambots. You need JavaScript enabled to view it. 
tel: +48 (22) 597 0742; fax: +48 (22) 597 0715

Degrees:
2009 PhD in Biological Engineering and Agronomic Sciences at the Institute of Life Sciences, Molecular Physiology Group (FYMO), Catholic University of Louvain, Belgium.
2006 Master of Advanced Science in Biological Engineering and Agronomic Sciences at the Catholic University of Louvain, Belgium.
2004 Master’s in Microbiology at the University of Wroclaw, Poland.

Research experience:
2009-2017 Postdoctoral fellow at the Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Germany.
2004-2008 PhD studies at the Institute of Life Sciences, Molecular Physiology Group (FYMO), Catholic University of Louvain, Belgium.

Achievements:
2018 EMBO Installation Grant
2017 NCN Opus 12
2005 PhD Fellowship from the FNRS-Fund for Scientific Research, Belgium
2004 ERASMUS Scholarship

Publications:
*(co-first authorship)

Koyuncu S, Saez I, Lee HJ, Gutierrez-Garcia R, Pokrzywa W, Fatima A, Hoppe T, Vilchez D. (2018). The ubiquitin ligase UBR5 suppresses proteostasis collapse in pluripotent stem cells from Huntington's disease patients. Nat Commun. 9(1):2886.

Balaji V, Pokrzywa W, Hoppe T. (2018). Ubiquitylation Pathways In Insulin Signaling and Organismal Homeostasis. Bioessays 40(5):e1700223.

Pokrzywa W, Hoppe T. (2017). CHIPped balance of proteostasis and longevity. Oncotarget 27: 96472-96473.

Pokrzywa W, Lorenz R, Hoppe T. (2017). Chaperone-directed ubiquitylation maintains proteostasis at the expense of longevity. Worm 6: e1371403.

Kevei É, Pokrzywa W*, Hoppe T. (2017). Repair or destruction-an intimate liaison between ubiquitin ligases and molecular chaperones in proteostasis. FEBS Lett. 591: 2616-2635.

Riga T, Pokrzywa W*, Kevei E, Akyuz M, Balaji V, Adrian S, Hoehfeld J, Hoppe T. (2017). The ubiquitin ligase CHIP integrates proteostasis and aging by regulation of insulin receptor turnover. Cell 169: 470-482.

Ackermann L, Schell M, Pokrzywa W, Gartner A, Schumacher B, Hoppe T. (2016). E4 ubiquitin ligase specific degradation hubs coordinate DNA double strand break repair and apoptosis. Nat. Struct. Mol. Biol. 23: 995-1002.

Frumkin A, Dror S, Pokrzywa W, Bar-Lavan Y, Karady I, Hoppe T, Ben-Zvi A. (2014). Challenging muscle homeostasis uncovers novel chaperone interactions in Caenorhabditis elegans. Front. Mol. Biosci. 1:21. 10.3389

Bonizec M, Hérissant L, Pokrzywa W, Geng F, Wenzel S, Howard G.C, Rodriguez P, Krause S, Tansey W.P, Hoppe T, Dargemont C. (2014). The ubiquitin-selective chaperone Cdc48/p97 associates with Ubx3 to modulate monoubiquitylation of histone H2B. Nucleic Acids Res. 42: 10975-10986.

Segref A, Kevei E, Pokrzywa W, Mansfeld J, Schmeisser K, Livnat-Levanon N, Ensenauer R, Glickman M.H, Ristow M, Hoppe T. (2014). Pathogenesis of human mitochondrial diseases is modulated by reduced activity of the ubiquitin/proteasome-system. Cell Metab. 4: 642-652.

Pokrzywa W, Hoppe T. (2013). Chaperoning myosin assembly in muscle formation and aging. Worm 2: e25644.

Gazda L, Pokrzywa W*, Hellerschmied D, Loewe T, Forné I, Mueller-Planitz F, Hoppe T, Clausen T. (2013). The myosin chaperone UNC-45 is organized in tandem modules to support myofilaments formation in C. elegans. Cell 153: 183-195.

Pokrzywa W, Guerriat B, Dodzian J, Morsomme P. (2009). Dual sorting of the Saccharomyces cerevisiae vacuolar protein Sna4p. Eukaryot. Cell 8: 278-286.

Stawiecka-Mirota M, Pokrzywa W*, Morvan J, Zoladek T, Haguenauer-Tsapis R, Urban-Grimal D, Morsomme P. (2007). Binding to Rsp5p targets to the endosomal pathway the yeast Sna3p, a protein ubiquitylated with Lysine-63-linked chains. Traffic 8: 1280-1296.

     The proteome is defined as the entire set of proteins that are expressed in a given cell type or organism, which can vary with time and physiological status. Quality control networks support the integrity of the cellular proteome. The human protein homeostasis network (proteostasis) involves >1000 accessory factors and regulatory components that govern protein synthesis, folding, and degradation. Defective folding can result in the greater abundance of toxic protein aggregates, which can endanger the integrity of the entire proteome. With age, the ability of post-mitotic cells to maintain a balanced proteome is gradually compromised, particularly by the downregulation of molecular chaperones and lower efficiency of protein degradation. As such, impairments in proteostasis are a major hallmark of aging and associated with dementia, neurodegeneration, type 2 diabetes, cystic fibrosis, cancer, and cardiovascular disease (Labbadia and Morimoto, 2015). One of the central nodes of the eukaryotic proteostasis network is the interaction between molecular chaperones and proteolytic machineries. To maintain the cellular proteome, molecular chaperones and ubiquitin‐dependent degradation pathways (ubiquitin/proteasome system [UPS]) coordinate protein refolding and the removal of terminally damaged proteins. Irreversibly affected proteins are recognized by chaperone‐assisted E3 ubiquitin ligases, which target them for degradation by the UPS or autophagy (Fig. 1).
     Our research concentrates on the basic understanding of the spatiotemporal regulation of protein quality control activity and substrate processing. We use cell culture systems and Caenorhabditis elegans as an ideal animal model to study the organismal regulation of stress responses and proteostasis.

Pokrzywa Fig.1

Fig. 1. The proteostasis network integrates chaperone pathways for the folding of newly synthesized proteins, for the remodeling of misfolded states, and for disaggregation with protein degradation that is mediated by the UPS and autophagy system. Approximately 180 different chaperone components and their regulators orchestrate these processes in mammalian cells, whereas the UPS comprises ∼600 different components, and the autophagy system comprises ∼30 different components. Figure from Harlt et al., 2011.

We focus mainly on the following projects:

1. Identification of signals that coordinate the function of distinct E3 ligases
     The UPS is a major proteolytic route that maintains the proteome during development, stress, and aging. Protein degradation is mainly mediated by the 26S proteasome upon the covalent attachment of ubiquitin to target proteins by E1 (activating), E2 (conjugating), and E3 (ligating) enzymes in a process known as ubiquitylation. Despite many structurally unrelated substrates, ubiquitin conjugation is remarkably selective. E3 ubiquitin ligases represent the largest group of proteins within the UPS, which is linked to their crucial role in substrate selection. A detailed analysis of several classes of E3 ligases identified specific proteins and molecular pathways that they regulate. Furthermore, the heterotypic oligomerization of E3 ligases might control the specificity and processivity of ubiquitylation. Recently, Scott and co-workers reported that two distinctive E3s could reciprocally monitor each other for the simultaneous and joint regulation of substrate ubiquitylation. Cullin-RING (CRL) ligase was shown to associate with a mechanistically distinct thioester-forming RBR-type E3, ARIH1, and rely on ARIH1 to directly add ubiquitin chains on CRL substrates (Scott et al., 2016). Therefore, the existence of cooperation between various E3 enzymes, which increases their molecular capabilities, appears to be highly probable but requires further exploration.
    
Our long-term objective is to understand the mechanistic and developmental aspects of protein degradation pathways that are defined by a specific pair of E3 enzymes. The combination of biochemical, microscopic, and genetic techniques with tissue-specific approaches in C. elegans will allow us to understand the ways in which alternative combinations of E3 proteins fine-tune proteolytic networks.

2. Stress-induced myosin folding and assembly mechanisms.
     The assembly and maintenance of myofilaments require a tightly balanced proteostasis network. One key player in myosin organization and muscle thick filament formation in health and disease is the Hsp90 co-chaperone UNC-45.
     The activity and assembly of various myosin subtypes are coordinated by conserved UCS (UNC-45/CRO1/She4p) domain proteins. One founding member of the UCS family is the Caenorhabditis elegans UNC-45, a protein that is essential for the organization of striated muscle filaments (Price et al., 2002). Moreover, UNC-45 homologs exist in vertebrates, indicating a conserved requirement for myosin-specific co-chaperones (Price et al., 2002). Indeed, abnormal UNC-45 function is associated with severe muscle defects that result in skeletal and cardiac myopathies (Janiesch et al., 2007).
     The integrity of sarcomeric structures is permanently challenged upon muscle growth and mechanical stress. In response to eccentric exercise or damage to myofibers, UNC-45 and the chaperone Hsp90 shuttle between the impaired myofibers to support their repair (Fig. 2). However, little is known about the coordination of protein homeostasis pathways upon mechanical stress. Therefore, the long-term objective of this project is to understand the ways in which the balance between protein folding and degradation networks is coordinated with myosin assembly and muscle integrity. We combine genetic and biochemical approaches to study the conserved function of UNC-45 in myosin assembly and examine the ways in which this function is modulated during mechanical stress. Specifically, we plan to use targeted screening strategies to uncover mechanosensory proteins, chaperones, and UPS and autophagy components that are required for muscle function. The conserved regulation of proteostasis networks is studied in C. elegans, C2C12 mouse myoblasts, and human skeletal muscles. Finally, we want to investigate the remodeling of UNC-45 folding machinery under mechanical stress. A combination of genetic, biochemical, and in vivo imaging techniques will allow us to examine stress-induced changes in protein folding and degradation pathways. The proposed research will have broad implications for our understanding of myosin assembly, human myopathies, and proteostasis mechanisms in general.

Fig.2Fig. 2. Model of UNC-45 polymerization in response to stress. The sarcomeric unit is defined by the distance between two Z-discs, including the A-band, I-band, and M-line. UNC-45 is composed of tandem modules that allow the simultaneous binding of Hsp70/Hsp90 and myosin, enabling the folding and assembly of myosin in regular spacing. In the fully developed muscle, UNC-45 might be stored on the Z-disk in its monomeric form, whereas the stress-induced relocation of UNC-45 to growing or damaged myofilaments might facilitate the assembly of polymeric UNC-45 chains. Figure adapted from Pokrzywa and Hoppe, 2013.