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Role of tau phosphorylation in formation of tau envelopes
Karhanová, Adéla ; Lánský, Zdeněk (advisor) ; Štěpánek, Luděk (referee)
Tau is an intrinsically-disordered microtubule-associated protein important for axonal development and a critical regulator of microtubule functions in axons. Tau activity is controlled by phosphorylation and its deregulation resulting in tau hyperphosphorylation and aggregation has been linked to multiple neurodegenerative disorders, collectively termed tauopathies. On microtubules, tau molecules segregate into two kinetically distinct phases, consisting of either independently diffusing molecules or interacting molecules that form cohesive "envelopes" around microtubules. Tau envelopes regulate the action of other microtubule-associated proteins, such as the motility of molecular motors, and protect microtubules against degradation by microtubule-severing enzymes. How the formation, dynamics, and function of tau envelopes are regulated, however, is unknown. Here we show that tau phosphorylation impedes the formation and functioning of protective tau envelopes. Using a combination of reconstitution experiments and live cell imaging, we show that phosphorylated tau incorporates into tau envelopes and that it slows down the envelope growth. Importantly, we demonstrate that phosphorylated tau also destabilizes already existing envelopes leading to their disassembly. Together, our results demonstrate...
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MAP code and regulation of microtubule-based processes
Karhanová, Adéla ; Lánský, Zdeněk (advisor) ; Tomášová, Štěpánka (referee)
Microtubule associated proteins (MAPs) are considered as key regulators of molecular trafficking in cells. Even though their malfunctioning results in severe pathologies, such as neurodegenerative disorders, the regulatory roles of these proteins remain under debate. Since MAPs bind to the cytoskeleton, this structure has to be vital for the function of MAPs. Microtubules, a highly dynamic type of cytoskeletal structure, have been given extra attention due to their association with cell division and vital functions in neurons. Microtubules can undergo post-translational modifications that affect molecular motors as well as binding of other proteins, such as MAPs. Whether post-translational modifications of microtubules regulate the distribution of MAPs is so far not sufficiently documented. However, MAPs have been shown to cooperatively form cohesive envelopes on the microtubules and thereby regulate the access of motors and severing enzymes. As there are many types of MAPs and they are mutually exclusive, a hypothesis of a regulatory 'MAP code' emerged recently in the literature. Using available literature, this review will try to introduce the new model of MAP code and provide some background information on previous research on this topic.
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