@phdthesis{Engelmann2023,
  author    = {Engelmann, Daria Marie},
  title     = {Regulation of Mammalian Phosphoglycolate Phosphatase},
  doi       = {10.25972/OPUS-19957},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-199577},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2023},
  abstract  = {Mammalian phoshoglycolate phosphatase (PGP, also known as AUM) belongs to the ubiquitous HAD superfamily of phosphatases. As several other members of HAD phosphatases, the Mg2+-dependent dephosphorylation is conducted via a nucleophilic attack from a conserved aspartate residue in the catalytic cleft. The protein structure of PGP could not yet be solved entirely. Only a hybrid consisting of the PGP cap and the PDXP core (pyridoxal phosphatase, closest enzyme paralog) was crystallizable so far. PGP is able to efficiently dephosphorylate 2-phosphoglycolate, 2-phospho-L-lactate, 4-phospho-D-erythronate, and glycerol-3-phosphate in vitro which makes them likely physiological substrates. The first three substrates can be derived from metabolic side reactions (during glycolysis) and inhibit key enzymes in glycolysis and pentose phosphate pathway, the latter is situated at the intersection between glycolysis and lipogenesis. 2-phosphoglycolate can also be released in the context of repair of oxidative DNA damage. The activity of purified PGP can be reversibly inhibited by oxidation - physiologically likely in association with epidermal growth factor (EGF) signal transduction. In fact, an association between persistently lacking PGP activity (via downregulation) and the presence of hyperphosphorylated proteins after EGF stimulation has been identified. Reversible oxidation and transient inactivation of PGP may be particularly important for short-term and feedback regulatory mechanisms (as part of the EGF signaling). Furthermore, cellular proliferation in PGP downregulated cells is constantly reduced. Whole-body PGP inactivation in mice is embryonically lethal. Despite the many well-known features and functions, the knowledge about PGP is still incomplete. In the present work the influence of reactive oxygen species (ROS) on PGP activity in cells und a possible connection between oxidative stress and the proliferation deficit of PGP downregulated cells was investigated. For the experiments, a spermatogonial cell line was used (due to the high PGP expression in testis). PGP activity can be reversibly inhibited in cellular lysates by H2O2 (as a ROS representative). Reversible oxidation could thus indeed be physiologically important. More oxidative DNA damage (by bleomycin) showed no PGP-dependent effects here. EGF stimulation (as an inducer of transient and well-controlled ROS production), low concentrations of menadione (as an oxidant) and N-acetylcysteine (as an antioxidant) were able to approximate the proliferation rate in PGP downregulated cells to that of control cells. The redox regulation of PGP could thus have an influence on cellular proliferation as a feedback mechanism - a mechanism that could not take place in PGP downregulated cells. However, the connections are probably even more complex and cannot be elucidated by a sole examination of the proliferation rate. The present results can thus only be regarded as preliminary experiments. For a better understanding of the features and functions of PGP, this work then focused on specific regulation of enzyme activity by pharmacologically applicable small molecules. Four potent inhibitors had previously been identified in a screening campaign. In this work, three of these four inhibiting compounds could be further characterized in experiments with highly purified, recombinant murine and human PGP. Compounds \#2 and \#9 showed competitive inhibition properties with a markedly rising KM value with little or no change in vmax. The results were consistent for all tested protein variants: the murine and the human PGP as well as a PGP/PDXP hybrid protein. Compound \#1 was the most potent and interesting PGP-inhibitory molecule: less change in KM and a constant decrease in vmax as well as a lower impact on the PGP/PDXP hybrid hint at a mixed mode of inhibition as a combination of competitive and non-competitive inhibition. The characterization of the potential inhibitors can serve as a basis for further structural analysis and studies on the complex physiological role of PGP.},
  subject      = {Phosphoglykolatphosphatase},
  language  = {en}
}
@phdthesis{Kaestner2023,
  author    = {Kaestner, Alexandra Annika Nadine},
  title     = {Charakterisierung pharmakologischer Phosphoglykolatphosphatase-Inhibitoren},
  doi       = {10.25972/OPUS-27239},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-272394},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2023},
  abstract  = {In dieser Arbeit geht es um die Phosphoglykolatphosphatase (PGP), die als Phosphatase vom Haloazid Dehalogenase-Typ (HAD-Phosphatase) zu der ubiquit{\"a}r vorkommenden Superfamilie der HAD-Hydrolasen geh{\"o}rt. In der Literatur ist eine in vitro Phosphatase-Aktivit{\"a}t gegen{\"u}ber 2-Phospho-L-Laktat (2PL), 4-Phospho-D-Erythronat (4PE), Phosphoglykolat (PG) und Glycerol-3-Phosphat (G3P) beschrieben. 2PL und 4PE entstehen in Nebenreaktionen w{\"a}hrend der Glykolyse und hemmen bei Akkumulation die Glykolyse bzw. den Pentosephosphatweg. PG kann auch in einer Nebenreaktion w{\"a}hrend der Glykolyse oder im Rahmen der Reparatur von oxidativen DNA-Sch{\"a}den entstehen. G3P entsteht aus Dihydroxyacetonphosphat und bildet das Kohlenhydratger{\"u}st der Triacylglyceride (TAG). Zellul{\"a}re Studien konnten Hinweise auf die Regulierung des epidermalen wachstumsfaktor-(EGF-)induzierten Zytoskelettumbaus durch die PGP liefern und die Untersuchung von M{\"a}usen mit PGP-Inaktivierung zeigte einen Einfluss auf die Zellproliferation und embryonale Entwicklung. Die Regulation der PGP-Expression f{\"u}hrte zu Ver{\"a}nderungen im Kohlenhydrat- und Fettstoffwechsel. Die Untersuchung der PGP-Funktionen erfolgte bislang ausschließlich mit genetischen Ans{\"a}tzen. Aufgrund von m{\"o}glichen Kompensationsmechanismen und Off-Target-Effekten m{\"u}ssen genetische und pharmakologische Methoden als sich erg{\"a}nzende Ans{\"a}tze verstanden werden. Um die Funktionen der PGP besser zu verstehen, fokussiert sich die vorliegende Arbeit auf die gezielte pharmakologische PGP-Inhibition. In Vorarbeiten wurden 41.000 Molek{\"u}le gescreent und f{\"u}nf potentielle Inhibitoren identifiziert. Ziele dieser Arbeit waren zum einen die Implementierung der Inhibitor \# 1-Behandlung in der Zellkultur, zum anderen die Charakterisierung der PGP-Hemmung durch Inhibitor \# 48 und die Durchf{\"u}hrung erster Selektivit{\"a}tstestungen mit Inhibitor \# 48. Zusammenfassend kann festgehalten werden, dass Inhibitor \# 1 in der Lage ist, die endogene PGP in Zelllysaten der murinen spermatogonialen Zelllinie (GC1) zu hemmen. Unter bestimmten Bedingungen f{\"u}hrte die Inhibitor \# 1-Behandlung der GC1-Zellen zur Hemmung der PGP. Erste Analysen zellul{\"a}rer Inhibitoreffekte konnten eine Steigerung der TAG-Konzentration in behandelten GC1-Zellen nachweisen. Die PGP-Hemmung durch Inhibitor \# 48 wurde als unkompetitive Inhibition charakterisiert und es zeigten sich keine relevanten Inhibitoreffekte auf die HAD-Phosphatasen Magnesium-abh{\"a}ngige Phosphatase 1 (MDP1), Lysin-Histidin-Pyrophosphat-Phosphatase (LHPP) und Polynukleotidase 5'-Kinase/3'-Phosphatase (PnkP). Dagegen konnte eine Aktivit{\"a}tssteigerung von Phospho 2 beobachtet werden. Die vorliegende Arbeit liefert somit erste Erkenntnisse {\"u}ber die Anwendung des PGP-Inhibitors \# 1 in der Zellkultur und schafft die Grundlage f{\"u}r nachfolgende Untersuchungen mit Inhibitor \# 48. Weitere Experimente sind notwendig, die die Inhibitorbehandlung in der Zellkultur optimieren und die Selektivit{\"a}t weiter charakterisieren, um mithilfe der Inhibitoren neue Erkenntnisse {\"u}ber die physiologische und pathophysiologische Rolle der PGP gewinnen zu k{\"o}nnen.},
  subject      = {Phosphoglykolatphosphatase},
  language  = {de}
}