STRUCTURAL AND FUNCTIONAL EFFECTS OF PARKINSON’S DISEASE-ASSOCIATED TENEURIN-4 VARIANTS

Sometimes, even subtle structural changes in brain proteins can contribute to development of various brain disorders. Teneurins are large synaptic adhesion proteins that play key roles in neuronal development, axon guidance and connectivity at neuronal synapses, enabled by the conformational adaptability of their extracellular architecture. Genetic variants of Teneurin-4 (Ten-4) have recently been identified in Parkinson’s Disease (PD) cohorts. Understanding structure and conformational behavior of those protein variants can help elucidating molecular mechanisms that connect genetic variations to disease-related dysfunctions. Here, we investigated how different PD-associated missense mutations affect structure, stability and cellular interactions of Ten-4. Using small-angle X-ray scattering (SAXS) and thermal stability assays, we assessed conformational variability and stability of Ten-4 variants in solutions, which was complemented by cellular interactions assays. SAXS revealed that most variants adopt a surprisingly more compact dimeric architecture compared to the wild-type, which correlated with the mutants’ enhanced thermal stability. Temperature-dependent measurements at wider scattering angles revealed additional insights into unfolding kinetics and internal packing rearrangements across different variants. Moreover, while wild-type Ten-4 showed pronounced stabilization in response to environmental modulation (gradual calcium-induced stability), mutants showed reduced responsiveness, consistent with higher-rigidity architecture. At last, cell-clustering assays demonstrated altered trans-cellular interactions for a subset of variants, pointing at functional consequences of these conformational shifts. Together, these results demonstrate that disease-linked mutations inducing even subtle shifts in protein conformation can affect its stability and further functional consequences. We propose that mutation-induced rigidification of Ten-4 can limit its physiological structural plasticity required for synaptic adhesion.