GTPase function of Leucine rich repeat kinase 2

LRRK 2基因突变是帕金森病的常见原因。该基因的蛋白产物具有激酶和GT3活性。由于激酶和GT3结构域都有突变，我们认为这两种活性可能在帕金森病的发病机制中很重要。因此，我们试图依次理解每一种活动以及它们如何相互作用。 我们与印第安纳州大学的Quyen Hoang合作，发现GT3（ROC）结构域的突变延长了LRRK 2处于活性状态的时间。使用生物化学的方法，我们现在已经表明，GTP水解GDP驱动二聚体，我们假设是无活性的，分解成单体，推测是活性的。降低GT3活性的突变有利于单体状态。这反映在LRRK 2蛋白在细胞中的trans-Golgi网络处的积累中。 我们已经使用类似的测定来正式比较小鼠和人LRRK 2的性质。也许令人惊讶的是，这两种同源物具有完全不同的特性，人类蛋白质比小鼠蛋白质更不稳定，更活跃。我们在这里的部分动机是试图了解一种风险因素变异的影响，这种变异在某些人群中相对常见，G2385 R，但在小鼠和人类LRRK 2之间并不保守。我们发现人类LRRK 2中的G2385 R导致蛋白质变得不太稳定，但在小鼠中类似的取代E2385 R没有我们可以测量的影响。这些结果可能表明为什么在小鼠中模拟LRRK 2突变效应具有挑战性。

LRRK2 gene mutations are a common cause of Parkinsons disease. The protein product of the gene has both kinase and GTPase activities. Because there are mutations in both kinase and GTPase domains, we consider that both activities are probably important for pathogenesis of Parkinsons disease. As such, we are trying to understand each activity in turn and how they interact. We have shown, in collaboration with Quyen Hoang at Indiana University, that mutations in the GTPase (ROC) domain prolong the time in which LRRK2 is in the active state. Using biochemical approaches, we have now shown that GTP hydrolysis to GDP drives dissociation of dimers, which we presume are inactive, into monomers, presumably active. Mutations that lower GTPase activity favor the monomeric state. This is reflected in accumulation of LRRK2 protein at the trans-Golgi network in cells. We have used similar assays to formally compare properties of mouse and human LRRK2. Perhaps surprisingly, the two homologues have quite different properties, with human protein being less stable and more active than the mouse counterpart. Part of our motivation here was to try and understand the effects of a risk factor variant that is relatively common in some populations, G2385R, but is not conserved between mouse and human LRRK2. We found that G2385R in human LRRK2 causes the protein to become less stable but that a similar substitution in mice, E2385R, had no effect that we could measure. These results may indicate why it has been challenging to model LRRK2 mutational effects in mice.