The Ykt6 SNARE protein is widely recognized as one of the most highly conserved SNARE proteins found. When it is active between the cytosol and membrane-bound compartments, it plays a critical role in vesicular fusion and trafficking in mainly yeast and mammalian cells. SNARE proteins are involved in many ways, from the transport of hormones to synaptic vesicle release and neuronal communication. SNARE proteins are comprised of more than 60 types within eukaryotic cells that allow for the fusion of two membranes in response to calcium and other excitatory molecules. The availability of these essential proteins could determine whether essential neurotransmitters or hormones are no longer regulated. This could mean the risk of hormonal toxicity, and imbalance which in turn can lead to worse problems for the patient. Thus, the role of SNARE proteins such as Ykt6 is essential for the balance within many diverse and complex bodily systems.
In the paper, “A conformational switch driven by phosphorylation regulates the activity of the evolutionary conserved SNARE Ykt6” by Dr. Takahashi and her colleagues, they set out to determine the mechanism behind the regulation of the SNARE Ykt6 protein. In their research, they also investigated the effects of phosphorylation on the protein regarding its function and role in vesicle trafficking. It was found that upon phosphorylation of the SNARE protein Ykt6, it would undergo a conformational change that would be from a closed cytosolic state to an open membrane-bound state. As stated in the article, the open membrane-bound state of the protein would lead to toxicity in the Parkinson’s disease models that were used. Ykt6 is an essential SNARE protein in eukaryotic cells that contains a C-terminal lipid anchor motif that can be reserved. The first experiment used by Dr. Takahashi and her colleagues was done using human embryonic kidney cells where the Ytk6 was tagged with a fluorescent protein. The second experiment was done using a high-content kinase screen assay in an effort to identify which kinase (s) were responsible for the phosphorylation of Ykt6 and its location in the cytosol versus the membrane. The third and final experiment that Dr. Takahashi and her colleagues conducted involved the use of an NMR in solution to measure the effect of S174 phosphorylation on Ykt6. Dr. Takahashi et al. discovered that there were profound impairments in the secretory pathway throughout the shift in equilibrium between a phosphorylated and dephosphorylated state. It was also found that the Ykt6 conformational change by phosphorylation is also an important regulatory step that often mediates autophagosome and secretory machinery.
In the paper, “Stress-induced cellular clearance is mediated by SNARE protein Ykt6 and disrupted by a-synuclein”by Dr. Cuddy and her colleagues, researchers set out to determine the mechanisms behind the role of Ykt6 in Parkinson’s disease patient cultures to its potential as a therapeutic target. This research was conducted to possibly enhance lysosomal activity and reduce protein accumulation. The first experiment that was conducted was done by the examination of lysosomal function in PD patient-derived iPSC-midbrain neurons (iPSn) to measure the effects of pathological aggregates on protein homeostasis. The second experiment that was conducted examined the levels of SNARE proteins that function in vesicle trafficking between the ER and Golgi. This was done using a Western blot analysis of various binding sites. The third experiment sought to determine if FTIs could have an effect on Ykt6 in the brains of mice. This was done by testing their effect on wild-type animals. Dr. Cuddy and her colleagues found in their research that the SNARE protein Ykt6 responds to lysosomal stress by mechanisms and processes that are regulated by post-translational prenylation. It was also found in the human midbrain models that were used, that lysosomal function is highly sensitive to Ykt6 levels. Ykt6 often works as a buffer that senses metabolic stress and thus moves into membranes to increase vesicle trafficking and lysosomal activity. Therefore, the research conducted in this study examines and defines the mechanisms for normal and stressful conditions. Per the article, this exemplifies the complex and diverse role that SNARE proteins play in the varying metabolic needs of the autophagic-lysosomal system. And so, Dr. Cuddy and her colleagues have shown the effects of overexpression and activation in the SNARE protein Ykt6 in relation to aiding lysosomal activity in the neurons of Parkinson's disease patients while not effecting the levels of other membrane proteins or hormonal secretions.
References:
McGrath K, Agarwal S, Tonelli M, Dergai M, Gaeta AL, Shum AK, Lacoste J, Zhang Y, Wen W, Chung D, Wiersum G, Shevade A, Zaichick S, van Rossum DB, Shuvalova L, Savas JN, Kuchin S, Taipale M, Caldwell KA, Caldwell GA, Fasshauer D, Caraveo G. A conformational switch driven by phosphorylation regulates the activity of the evolutionarily conserved SNARE Ykt6. Proc Natl Acad Sci USA. 2021 Mar 23;118(12):e2016730118. doi: 10.1073/pnas.2016730118
Duda JE, Giasson BI, Mabon ME, Lee VM, and Trojanowski JQ. (2002). Novel antibodies to synuclein show abundant striatal pathology in Lewy body diseases. Ann Neurol 52, 205–210:
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