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Morbus Cushing ist die häufigste Ursache für endogenes Cushing-Syndrom und führt auf Grund eines kortikotropen Hypophysenadenoms zu einem Glucocorticoid Überschuss und wiederum zu einer hohen Morbidität und Mortalität. Die Ursache hierfür sind unter anderem somatische Mutationen in den Deubiquitinasen USP8 und USP48. Das Ziel dieser Arbeit war es mittels der CRISPR/Cas9-Methode, die Mutationen USP8 und USP48 in Zelllinien zu etablieren und diese für Cushing-Syndrom Analysen zu verwenden. Hierfür wurden in dieser Arbeit gRNAs für USP8 und USP48 designt, welche anschließend in die humane embryonale Zelllinie HEK293AD Zellen transfiziert wurden. Diese Zellen wurden zu monoklonalen Zellen vereinzelt. Ziel war einen Knock-out von USP8 bzw. USP48 zu generieren. Es konnte ein erfolgreicher Zellklon generiert werden mit einem Knock-out von USP48. Ebenfalls konnte ein Genomediting von USP8 in Exon 20 durchgeführt werden. Zusammenfassend konnte die CRISPR/Cas9 Methode für ein M. Cushing-Zellmodells etabliert und eine gute Ausgangsbasis für weitere Experimente (z.B. ein gezielter Knock-in von USP8- und USP48- Mutationen) generiert werden.
Adrenal Cushing’s Syndrome (CS) is a rare but life-threatening disease and therefore it is of great importance to understand the pathogenesis leading to adrenal CS. It is well accepted that Protein Kinase A (PKA) signalling mediates steroid secretion in adrenocortical cells. PKA is an inactive heterotetramer, consisting of two catalytic and two regulatory subunits. Upon cAMP binding to the regulatory subunits, the catalytic subunits are released and are able to phosphorylate their target proteins. Recently, activating somatic mutations affecting the catalytic subunit a of PKA have been identified in a sub-population of cortisol-producing adenomas (CPAs) associated with overt CS. Interestingly, the PKA regulatory subunit IIb has long been known to have significantly lower protein levels in a sub-group of CPAs compared to other adrenocortical tumours. Yet, it is unknown, why these CPAs lack the regulatory subunit IIb, neither are any functional consequences nor are the underlying regulation mechanisms leading to reduced RIIb levels known. The results obtained in this thesis show a clear connection between Ca mutations and reduced RIIb protein levels in CPAs but not in other adrenocortical tumours. Furthermore, a specific pattern of PKA subunit expression in the different zones of the normal adrenal gland is demonstrated. In addition, a Ca L206R mutation-mediated degradation of RIIb was observed in adrenocortical cells in vitro. RIIb degradation was found to be mediated by caspases and by performing mutagenesis experiments of the regulatory subunits IIb and Ia, S114 phosphorylation of RIIb was identified to make RIIb susceptible for degradation. LC-MS/MS revealed RIIb interaction partners to differ in the presence of either Ca WT and Ca L206R. These newly identified interaction partners are possibly involved in targeting RIIb to subcellular compartments or bringing it into spatial proximity of degrading enzymes. Furthermore, reducing RIIb protein levels in an in vitro system were shown to correlate with increased cortisol secretion also in the absence of PRKACA mutations. The inhibiting role of RIIb in cortisol secretion demonstrates a new function of this regulatory PKA subunit, improving the understanding of the complex regulation of PKA as key regulator in many cells.