A direct interaction between leucine-rich repeat kinase 2 and specific ß-tubulin isoforms regulates tubulin acetylation.

Mutations in LRRK2, encoding the multifunctional protein leucine-rich repeat kinase 2 (LRRK2), are a common cause of Parkinson disease. LRRK2 has been suggested to influence the cytoskeleton as LRRK2 mutants reduce neurite outgrowth and cause an accumulation of hyperphosphorylated Tau. This might cause alterations in the dynamic instability of microtubules suggested to contribute to the pathogenesis of Parkinson disease. Here, we describe a direct interaction between LRRK2 and ß-tubulin. This interaction is conferred by the LRRK2 Roc domain and is disrupted by the familial R1441G mutation and artificial Roc domain mutations that mimic autophosphorylation. LRRK2 selectively interacts with three ß-tubulin isoforms: TUBB, TUBB4, and TUBB6, one of which (TUBB4) is mutated in the movement disorder dystonia type 4 (DYT4). Binding specificity is determined by lysine 362 and alanine 364 of ß-tubulin. Molecular modeling was used to map the interaction surface to the luminal face of microtubule protofibrils in close proximity to the lysine 40 acetylation site in α-tubulin. This location is predicted to be poorly accessible within mature stabilized microtubules, but exposed in dynamic microtubule populations. Consistent with this finding, endogenous LRRK2 displays a preferential localization to dynamic microtubules within growth cones, rather than adjacent axonal microtubule bundles. This interaction is functionally relevant to microtubule dynamics, as mouse embryonic fibroblasts derived from LRRK2 knock-out mice display increased microtubule acetylation. Taken together, our data shed light on the nature of the LRRK2-tubulin interaction, and indicate that alterations in microtubule stability caused by changes in LRRK2 might contribute to the pathogenesis of Parkinson disease.

The Burden of a Multiple Myeloma Diagnosis on Patients and Caregivers in the First Year: Western European Findings.

Background: This research aimed to quantify the burden of illness (BoI) in transplant eligible (TE) and transplant non-eligible (TNE) newly diagnosed multiple myeloma (NDMM) patients and their caregivers, in the first year after diagnosis: at months 0, 3, and 12. Methods: Prospective, cross-sectional, observational NDMM study of TE and TNE patients and their caregivers from France, Germany, Italy, and Spain was conducted between May 2019 and January 2021. A structured, online questionnaire measuring disease burden, direct and costs, out-of-pocket expenses, and health-related quality of life (HRQoL) was used. Descriptive statistics were performed. Results: A total of 164, 160, and 190 NDMM patients [>65 years; self-described healthy; not working; living with caregiver] answered at months 0, 3, and 12. Patients lost independence to perform daily activities; mean pain intensity rose and opioid utilization increased, more significantly among TNE patients. Overall health status and HRQoL remained stable. Median 3-month direct medical costs peaked at month 3. Specialist consultations and hospital admissions were the greatest cost amongst TE and TNE patients. Home adaptations increased out-of-pocket expenditures amongst TNE patients. Patients describing themselves as working spent a median 0 hours in the office at all time points. A total of 131, 122, and 124 caregivers answered at months 0, 3, and 12. Mean self-rated burden score rose. By month 12, half of caregivers developed stress, anxiety or depression. Most employed caregivers continued working. Productivity was low at month 0 with a trend of recovering at month 12. Caregivers of TNE compared to TE patients reported greater time burden. Caregivers' HRQoL was stable over time. Conclusion: NDMM is burdensome for patients and caregivers in the first year after diagnosis. TNE patients are more dependent on caregivers and incur higher care costs than TE patients. Despite the financial, physical, and emotional burden, HRQoL remains stable possibly indicating resilience and illness adjustment amongst patients and caregivers.

Protective LRRK2 R1398H Variant Enhances GTPase and Wnt Signaling Activity.

Mutations in LRRK2 are a common cause of familial and idiopathic Parkinson's disease (PD). Recently, the LRRK2 GTPase domain R1398H variant was suggested in genetic studies to confer protection against PD but mechanistic data supporting this is lacking. Here, we present evidence that R1398H affects GTPase function, axon outgrowth, and Wnt signaling in a manner opposite to pathogenic LRRK2 mutations. LRRK2 R1398H GTPase domain dimerization and GTP hydrolysis were increased whereas GTP binding was reduced, leading to a decrease in active GTP-bound LRRK2. This protective variant also increased axon length of primary cortical neurones in comparison to wild-type LRRK2, whereas the R1441G LRRK2 pathogenic mutant decreased axon outgrowth. Importantly, R1398H enhanced the stimulatory effect of LRRK2 on canonical Wnt signaling whereas the G2385R risk variant, in accordance with all previously tested pathogenic LRRK2 mutants, had the opposite effect. Molecular modeling placed R1398H in close proximity to PD-causing mutations suggesting that this protective LRRK2 variant, like familial mutations, affects intramolecular RocCOR domain interactions. Thus, our data suggest that R1398H LRRK2 is a bona fide protective variant. The opposite effects of protective versus PD associated LRRK2 variants on GTPase function and canonical Wnt signaling activity also suggests that regulation of these two basic signaling mechanisms is important for neuronal function. We conclude that LRRK2 mediated Wnt signaling and GTPase function are fundamental in conferring disease susceptibility and have clear implications for therapeutic target identification.