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Kinesin-mediated transport along microtubules is critical for axon development and health. Mutations in the kinesin Kif21a, or the microtubule subunit β-tubulin, inhibit axon growth and/or maintenance resulting in the eye-movement disorder congenital fibrosis of the extraocular muscles (CFEOM). While most examined CFEOM-causing β-tubulin mutations inhibit kinesin–microtubule interactions, Kif21a mutations activate the motor protein. These contrasting observations have led to opposed models of inhibited or hyperactive Kif21a in CFEOM. We show that, contrary to other CFEOM-causing β-tubulin mutations, R380C enhances kinesin activity. Expression of β-tubulin-R380C increases kinesin-mediated peroxisome transport in S2 cells. The binding frequency, percent motile engagements, run length and plus-end dwell time of Kif21a are also elevated on β-tubulin-R380C compared with wildtype microtubules in vitro. This conserved effect persists across tubulins from multiple species and kinesins from different families. The enhanced activity is independent of tail-mediated kinesin autoinhibition and thus utilizes a mechanism distinct from CFEOM-causing Kif21a mutations. Using molecular dynamics, we visualize how β-tubulin-R380C allosterically alters critical structural elements within the kinesin motor domain, suggesting a basis for the enhanced motility. These findings resolve the disparate models and confirm that inhibited or increased kinesin activity can both contribute to CFEOM. They also demonstrate the microtubule’s role in regulating kinesins and highlight the importance of balanced transport for cellular and organismal health.
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Computational analysis of hereditary spastic paraplegia mutations in the kinesin motor domains of KIF1A and KIF5A
• The structure-based energy calculations were applied to determine the effects of disease-causing kinesin missense mutations on protein stability and protein-protein interaction. • The mutations associated with Intellectual Disability can decrease the protein stability of KIF1A motor domain. • Hereditary Spastic Paraplegia mutations located in kinesin-tubulin complex interface can destabilize the binding infinity of KIF5A-tubulin complex.
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- PAR ID:
- 10193600
- Date Published:
- Journal Name:
- Journal of Theoretical and Computational Chemistry
- Volume:
- 19
- Issue:
- 06
- ISSN:
- 0219-6336
- Page Range / eLocation ID:
- 2041003
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Kinesin motor proteins perform several essential cellular functions powered by the adenosine triphosphate (ATP) hydrolysis reaction. Several single-point mutations in the kinesin motor protein KIF5A have been implicated to hereditary spastic paraplegia disease (HSP), a lethal neurodegenerative disease in humans. In earlier studies, we have shown that a series of HSP-related mutations can impair the kinesin’s long-distance displacement or processivity by modulating the order–disorder transition of the linker connecting the heads to the coiled coil. On the other hand, the reduction of kinesin’s ATP hydrolysis reaction rate by a distal asparagine-to-serine mutation is also known to cause HSP disease. However, the molecular mechanism of the ATP hydrolysis reaction in kinesin by this distal mutation is still not fully understood. Using classical molecular dynamics simulations combined with quantum mechanics/molecular mechanics calculations, the pre-organization geometry required for optimal hydrolysis in kinesin motor bound to α/β-tubulin is determined. This optimal geometry has only a single salt-bridge (of the possible two) between Arg203-Glu236, putting a reactive water molecule at a perfect position for hydrolysis. Such geometry is also needed to create the appropriate configuration for proton translocation during ATP hydrolysis. The distal asparagine-to-serine mutation is found to disrupt this optimal geometry. Therefore, the current study along with our previous one demonstrates how two different effects on kinesin dynamics (processivity and ATP hydrolysis), caused by a different set of genotypes, can give rise to the same phenotype leading to HSP disease.more » « less
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Motor proteins are active enzymatic molecules that are critically important for a variety of biological phenomena. It is known that some neurodegenerative diseases are caused by specific mutations in motor proteins that lead to their malfunctioning. Hereditary spastic paraplegia is one of such diseases, and it is associated with the mutations in the neuronal conventional kinesin gene, producing the decreased speed and processivity of this motor protein. Despite the importance of this problem, there is no clear understanding on the role of mutations in modifying dynamic properties of motor proteins. In this work, we investigate theoretically the molecular basis for negative effects of two specific mutations, N256S and R280S, on the dynamics of kinesin motor proteins. We hypothesize that these mutations might accelerate the adenosine triphosphate (ATP) release by increasing the probability of open conformations for the ATP-binding pocket. Our approach is based on the use of coarse-grained structure-based molecular dynamics simulations to analyze the conformational changes and chemical transitions in the kinesin molecule, which is also supplemented by investigation of a mesoscopic discrete-state stochastic model. Computer simulations suggest that mutations N256S and R280S can decrease the free energy difference between open and closed biochemical states, making the open conformation more stable and the ATP release faster, which is in agreement with our hypothesis. Furthermore, we show that in the case of N256S mutation, this effect is caused by disruption of interactions between α helix and switch I and loop L11 structural elements. Our computational results are qualitatively supported by the explicit analysis of the discrete-state stochastic model.more » « less
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The delivery of intracellular cargoes by kinesins is modulated at scales ranging from the geometry of the microtubule networks down to interactions with individual tubulins and their code. The complexity of the tubulin code and the difficulty in directly observing motor‐tubulin interactions have hindered progress in pinpointing the precise mechanisms by which kinesin's function is modulated. As one such example, past experiments show that cleaving tubulin C‐terminal tails (CTTs) lowers kinesin‐1's processivity and velocity on microtubules, but how these CTTs intertwine with kinesin's processive cycle remains unclear. In this work, we formulate and interrogate several plausible mechanisms by which CTTs contribute to and modulate kinesin motion. Computational modeling bridges the gap between effective transport observations (processivity, velocities) and microscopic mechanisms. Ultimately, we find that a guiding mechanism can best explain the observed differences in processivity and velocity. Altogether, our work adds a new understanding of how the CTTs and their modulation via the tubulin code may steer intracellular traffic in both health and disease.more » « less
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1142/S0219633620410035
