DrosophilaAcyl-CoA Synthetase Long-Chain Family Member 4 Regulates Axonal Transport of Synaptic Vesicles and Is Required for Synaptic Development and Transmission

Abstract

Acyl-CoA synthetase long-chain family member 4 (ACSL4) converts long-chain fatty acids to acyl-CoAs that are indispensable for lipid metabolism and cell signaling. Mutations in ACSL4 cause nonsyndromic X-linked mental retardation. We previously demonstrated that Drosophila dAcsl is functionally homologous to human ACSL4, and is required for axonal targeting in the brain. Here, we report that Drosophila dAcsl mutants exhibited distally biased axonal aggregates that were immunopositive for the synaptic-vesicle proteins synaptotagmin (Syt) and cysteine-string protein, the late endosome/lysosome marker lysosome-associated membrane protein 1, the autophagosomal marker Atg8, and the multivesicular body marker Hrs (hepatocyte growth factor-regulated tyrosine kinase substrate). In contrast, the axonal distribution of mitochondria and the cell adhesion molecule Fas II (fasciclin II) was normal. Electron microscopy revealed accumulation of prelysomes and multivesicle bodies. These aggregates appear as retrograde instead of anterograde cargos. Live imaging analysis revealed that dAcsl mutations increased the velocity of anterograde transport but reduced the flux, velocity, and processivity of retrograde transport of Syt-enhanced green fluorescent protein-labeled vesicles. Immunohistochemical and electrophysiological analyses showed significantly reduced growth and stability of neuromuscular synapses, and impaired glutamatergic neurotransmission in dAcsl mutants. The axonal aggregates and synaptic defects in dAcsl mutants were fully rescued by neuronal expression of human ACSL4, supporting a functional conservation of ACSL4 across species in the nervous system. Together, our findings demonstrate that dAcsl regulates axonal transport of synaptic vesicles and is required for synaptic development and function. Defects in axonal transport and synaptic function may account, at least in part, for the pathogenesis of ACSL4-related mental retardation.

Acsl, the Drosophila ortholog of intellectual-disability-related ACSL4, inhibits synaptic growth by altered lipids

“…3). The two proteins also have conserved functions in other processes, such as lipid storage (Zhang et al, 2009), axonal transport and synaptic development (Liu et al, 2014(Liu et al, , 2011.…”

“…Immunostaining of larval preparations was performed as previously described (Liu et al, 2011(Liu et al, , 2014. Specimens were dissected in Ca…”

“…Drosophila Acsl, also known as dAcsl, is the ortholog of mammalian ACSL3 and ACSL4 (Zhang et al, 2009). We have previously reported that Acsl affects axonal transport of synaptic vesicles and inhibits NMJ growth by inhibiting bone morphogenetic protein (BMP) signaling (Liu et al, 2011(Liu et al, , 2014. However, how Acsl affects lipid metabolism and the role of Acsl-regulated lipid metabolism in synapse development are largely unknown.…”

Microtubule-severing protein Katanin regulates neuromuscular junction development and dendritic elaboration in Drosophila

“…Electron microscopy of NMJ terminals was performed largely according to previously published procedures Liu et al, 2011;. Ultrathin (70-80 nm) longitudinal sections of NMJ 6 or 7 from the abdominal segment A3 were cut with a Leica UC6 ultramicrotome.…”

Arachidonic acid in Alzheimer's disease

“…In addition to the ubiquitous isoform, a neuronal specific isoform was identified and differs from the first one by an additional 41 amino-acid N-terminal domain 17 . Mutant ACLS4 gene was associated to X-linked mental retardation 18 and has been involved in neuronal differentiation, axonal transportations and synapse formation 17,18,19 . Channeling of ARA by ACSL4 and Lysophosphatidylinositol-acyltransferase-1 (LPIAT1) to phosphatitylinositol (PI) has been described in CHO cells 20 .…”