Amyotrophic lateral sclerosis-associated mutant VAPBP56S perturbs calcium homeostasis to disrupt axonal transport of mitochondria.

Abstract

A proline-to-serine substitution at position 56 in the gene encoding vesicle-associated membrane protein-associated protein B (VAPB; VAPBP56S) causes some dominantly inherited familial forms of motor neuron disease, including amyotrophic lateral sclerosis (ALS) type-8. Here, we show that expression of ALS mutant VAPBP56S but not wild-type VAPB in neurons selectively disrupts anterograde axonal transport of mitochondria. VAPBP56S-induced disruption of mitochondrial transport involved reductions in the frequency, velocity and persistence of anterograde mitochondrial movement. Anterograde axonal transport of mitochondria is mediated by the microtubule-based molecular motor kinesin-1. Attachment of kinesin-1 to mitochondria involves the outer mitochondrial membrane protein mitochondrial Rho GTPase-1 (Miro1) which acts as a sensor for cytosolic calcium levels ([Ca(2+)]c); elevated [Ca(2+)]c disrupts mitochondrial transport via an effect on Miro1. To gain insight into the mechanisms underlying the VAPBP56S effect on mitochondrial transport, we monitored [Ca(2+)]c levels in VAPBP56S-expressing neurons. Expression of VAPBP56S but not VAPB increased resting [Ca(2+)]c and this was associated with a reduction in the amounts of tubulin but not kinesin-1 that were associated with Miro1. Moreover, expression of a Ca(2+) insensitive mutant of Miro1 rescued defective mitochondrial axonal transport and restored the amounts of tubulin associated with the Miro1/kinesin-1 complex to normal in VAPBP56S-expressing cells. Our results suggest that ALS mutant VAPBP56S perturbs anterograde mitochondrial axonal transport by disrupting Ca(2+) homeostasis and effecting the Miro1/kinesin-1 interaction with tubulin.

• Authors: Gábor M Mórotz, Kurt J De Vos, Alessio Vagnoni, Steven Ackerley, Christopher E Shaw, Christopher C J Miller
• Journal: Human molecular genetics (Hum Mol Genet) Vol. 21 Issue 9 Pg. 1979-88 (May 01 2012) ISSN: 1460-2083 [Electronic] England
• PMID: 22258555 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• KIF5B protein, human
• Mitochondrial Proteins
• Mutant Proteins
• Recombinant Proteins
• Tubulin
• VAPB protein, human
• Vesicular Transport Proteins
• RHOT1 protein, human
• Kinesins
• rho GTP-Binding Proteins
• Calcium

Topics

• Amino Acid Substitution
• Amyotrophic Lateral Sclerosis (genetics, metabolism)
• Animals
• Axonal Transport (genetics, physiology)
• Base Sequence
• Calcium (metabolism)
• HEK293 Cells
• Homeostasis
• Humans
• Kinesins (metabolism)
• Mitochondria (metabolism)
• Mitochondrial Proteins (genetics, metabolism)
• Movement
• Mutagenesis, Site-Directed
• Mutant Proteins (genetics, metabolism)
• Neurons (metabolism)
• Plasmids (genetics)
• Rats
• Recombinant Proteins (genetics, metabolism)
• Time-Lapse Imaging
• Transfection
• Tubulin (metabolism)
• Vesicular Transport Proteins (genetics, metabolism)
• rho GTP-Binding Proteins (genetics, metabolism)