Showing papers by "Georgia Sotiropoulou published in 2022"

Reconstructing the epidermal proteolytic cascades in health and disease

Abstract: The epidermis is the outer stratified epithelium of the skin, forming the physical barrier that is indispensable for homeostasis. Epidermal proteolysis, mainly but not exclusively executed by kallikrein‐related peptidases (KLKs), is tightly regulated to ensure maintenance of physiological skin renewal and an intact skin barrier. Perturbation of epidermal proteolytic networks is implicated in a wide array of rare and common skin pathologies of diverse genetic backgrounds. Recent studies of monogenic human skin diseases and newly developed animal models have revealed new mechanisms of regulation of proteolytic pathways in epidermal physiology and in disease states. These new data have challenged some accepted views, for example the role of matriptase in epidermal desquamation, which turned out to be restricted to mouse skin. The significance of PAR2 signaling in skin inflammation should also be reconsidered in the face of recent findings. Cumulatively, recent studies necessitate a sophisticated redefinition of the proteolytic and signaling pathways that operate in human skin. We elaborate how epidermal proteolysis is finely regulated at multiple levels, and in a spatial manner that has not been taken into consideration so far, in which specific proteases are confined to distinct epidermal sublayers. Of interest, transglutaminases have emerged as regulators of epidermal proteolysis and desquamation by spatially fixing endogenous protease inhibitors, constituting regulatory factors that were not recognized before. Furthermore, new evidence suggests a link between proteolysis and lipid metabolism. By synthesis of established notions and recent discoveries, we provide an up‐to‐date critical evaluation and synthesis of current knowledge and the extended complexity of proteolysis regulation and signaling pathways in skin. © 2022 The Pathological Society of Great Britain and Ireland.

Activity-Based Probes for Proteases Pave the Way to Theranostic Applications

Abstract: Proteases are important enzymes in health and disease. Their activities are regulated at multiple levels. In fact, proteases are synthesized as inactive proenzymes (zymogens) that are activated by proteolytic removal of their pro-peptide sequence and can remain active or their activity can be attenuated by complex formation with specific endogenous inhibitors or by limited proteolysis or degradation. Consequently, quite often, only a fraction of the protease molecules is in the active/functional form, thus, the abundance of a protease is not always linearly proportional to the (patho)physiological function(s). Therefore, assays to determine the active forms of proteases are needed, not only in research but also in molecular diagnosis and therapy. Activity-based probes (ABPs) are chemical entities that bind covalently to the active enzyme/protease. ABPs carry a detection tag to enable localization and quantification of specific enzymatic/proteolytic activities with applications in molecular imaging and diagnosis. Moreover, ABPs act as suicide inhibitors of proteases, which can be exploited for delineation of the functional role(s) of a given protease in (patho) biological context and as potential therapeutics. In this sense, ABPs represent new theranostic agents. We outline recent developments pertaining to ABPs for proteases with potential therapeutic applications, with the aim to highlight their importance in theranostics.

A chemogenomic approach is required for effective treatment of amyotrophic lateral sclerosis

Abstract: Abstract ALS is a fatal untreatable disease involving degeneration of motor neurons. Μultiple causative genes encoding proteins with versatile functions have been identified indicating that diverse biological pathways lead to ALS. Chemical entities still represent a promising choice to delay ALS progression, attenuate symptoms and/or increase life expectancy, but also gene‐based and stem cell‐based therapies are in the process of development, and some are tested in clinical trials. Various compounds proved effective in transgenic models overexpressing distinct ALS causative genes unfortunately though, they showed no efficacy in clinical trials. Notably, while animal models provide a uniform genetic background for preclinical testing, ALS patients are not stratified, and the distinct genetic forms of ALS are treated as one group, which could explain the observed discrepancies between treating genetically homogeneous mice and quite heterogeneous patient cohorts. We suggest that chemical entity‐genotype correlation should be exploited to guide patient stratification for pharmacotherapy, that is administered drugs should be selected based on the ALS genetic background.

Furthering Understanding of Aerosol-Cloud-Precipitation Interactions in the Arctic

Abstract: Conference Title: 2nd QuIESCENT (Quantifying the Indirect Effect: from Sources to Climate Effects of Natural and Transported aerosol in the Arctic) Workshop What: Atmospheric scientists, shared and discussed recent work to understand the complex interactions between aerosols, clouds, precipitation, radiation and dynamics at northern high latitudes, as well as recent and upcoming field campaigns to improve that understanding. When: 30 March – 1 April, 2022 Where: Tromsø, Norway

Novel specific activity-based probes validate KLK proteases as druggable targets

Abstract: Dear Editors We read with great interest the recent publication by Lee et al., in which the important paper by Lovell et al. is presented as the first report of activity-based protein profiling (ABPP) selective for individual KLKs in a complex biological context. Fairly, at the exact same time when the manuscript by Lovell et al. appeared, a novel KLK7-specific phosphonate activity-based probe (ABP) was reported, which could discriminate KLK7 from other active KLKs. That ABP was used to quantify the active KLK7 in situ, specifically, in the epidermis, in a pathological setting in which multiple KLK proteases are active and functionally implicated in disease. The KLK7-ABP was also modified to a quenched ABP (qABP) to enable monitoring of KLK7 activity in vivo. Notably, the KLK7-ABP rescued major disease hallmarks, when applied onto the epidermis of Spink5Klk5 mice. Spink5 mice represent an established preclinical model that recapitulates the overdesquamating and inflammatory skin disease named Netherton syndrome, a rare ichthyosis caused by inactivating mutations in SPINK5 encoding the LEKTI inhibitor of serine proteases. It is well established that LEKTI deficiency causes unopposed (disease causative) proteolytic activities in the epidermis. In Spink5Klk5, Klk5 was genetically ablated on the Netherton background to provide proof of concept for drugging the KLK5 activity for pharmacotherapy of Netherton syndrome and, potentially, other diseases like atopic dermatitis. The Spink5Klk5 model proved that KLK5 represents a novel drug target. Nevertheless, inhibition of KLK5 is not sufficient for permanent rescue/therapy of this very severe (potentially lethal) disease, since delayed inflammation develops soon in these mice due to KLK7 activity. This was also revealed by the fact that inhibition with the KLK7-ABP attenuates inflammation. Thus, additional targeting of inflammation is required in Spink5Klk5 with either KLK7 inhibitors or anti-TNFα biologics. Overall, these studies have provided a strong rational for drugging the KLK family and set the grounds for pharmaceutical development of the recently described boronate inhibitor for KLK5. For the first time, use of the KLK7-ABP (in combination with genetic knockout) allowed validation of the given KLK7 activity as a drug target in a well-established disease context in vivo and provided preclinical proof of concept for using ABPs targeting the KLKs as theranostics, namely dually exploitable for disease diagnosis and treatment. Previously, ABPs for cathepsins were used as theranostics and cancer imaging tools by the group of Galia Blum. Beyond these studies that established KLKs as druggable targets in skin pathologies, targeting KLKs for treatment of prostate cancer was the subject of studies performed more than a decade ago. Specifically, the prostate proteases KLK2 and KLK3 were exploited for activation of anticancer prodrugs developed for treatment of prostate cancer. Drugging KLKs for prostate cancer, for example, resulted in a boronic acidbased inhibitor of KLK3, while KLKs have been clinically tested by various approaches, and there have been success stories in this respect, PROSTVAC (an active immunotherapy vaccine that contains KLK3/PSA) being one such example. In contrast to the Lee et al. KLKs are druggable. Following mapping of the KLK gene cluster in 2000, extensive knowledge was accumulated on the abundance of immunoreactive KLKs in normal and cancer-related settings, revealing these enzymes as potential biomarkers and/or therapeutic targets for cancer but also other diseases, including viral infections of high current interest. This triggered attempts to quantify the active forms of KLK proteases in biological and clinical samples. Coordinated dysregulation of specific KLKs in disease states (including cancer, inflammation, and neurodegeneration) suggested that multiple KLK enzymes could interplay in the mode of “proteolytic cascades,” which could also crosstalk with proteases of differing specificities. It was proposed that specific regulatory KLK cascades could be functionally implicated in (patho)physiology in certain tissues like the skin and the prostate. Of note, a proteolytic cascade pathway involving KLK5 (and putatively other KLK proteases) was proposed to be implicated in prostate physiology (i.e., seminal clot liquefaction) and prostate cancer progression, originally by Michael et al., more than 15 years ago. In fact, the prime attempt to quantify the proportion of enzymatically active KLK6 relative to total immunoreactive KLK6 was in 2008, by Oikonomopoulou et al., who developed an ELISA using an ABP that targets trypsin-like serine proteases,