Axonal Gradient of Arachidonic Acid-containing Phosphatidylcholine and Its Dependence on Actin Dynamics

Hyun-Jeong Yang,Yuki Sugiura,Koji Ikegami,Yoshiyuki Konishi,Mitsutoshi Setou

doi:10.1074/jbc.m111.316877

Hyun-Jeong Yang, Yuki Sugiura + Show 3 more

Open Access

https://doi.org/10.1074/jbc.m111.316877

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Abstract

Phosphatidylcholine (PC) is the most abundant component of lipid bilayers and exists in various molecular forms, through combinations of two acylated fatty acids. Arachidonic acid (AA)-containing PC (AA-PC) can be a source of AA, which is a crucial mediator of synaptic transmission and intracellular signaling. However, the distribution of AA-PC within neurons has not been indicated. In the present study, we used imaging mass spectrometry to characterize the distribution of PC species in cultured neurons of superior cervical ganglia. Intriguingly, PC species exhibited a unique distribution that was dependent on the acyl chains at the sn-2 position. In particular, we found that AA-PC is enriched within the axon and is distributed across a proximal-to-distal gradient. Inhibitors of actin dynamics (cytochalasin D and phallacidin) disrupted this gradient. This is the first report of the gradual distribution of AA-PC along the axon and its association with actin dynamics.

Highlights

The neuronal distribution of arachidonic acid-containing phosphatidylcholine (AA-PC) remains unknown
Our data demonstrate that compared with saturated fatty acid (SA)/monounsaturated fatty acid (MUSA)/linoleic acid (LA)-PCs, Arachidonic acid (AA)-PC is highly localized in the axon rather than in the cell body
Possible Biological Function of Axonal Gradient of AA-PC— AA-PC(diacyl-38:4) is a major PC species in superior cervical ganglia (SCG) neurons, and its acyl chains were assigned as PC(diacyl-18:0/20:4) (Table 1) based on evidence indicating that endogenous PC possesses PUFAs at sn-2 positions rather than at sn-1 positions [18]

Summary

Background

The neuronal distribution of arachidonic acid-containing phosphatidylcholine (AA-PC) remains unknown. Results: AA-PC axonal intensity showed a proximal-to-distal gradient, which was disrupted by actin inhibitors. We used imaging mass spectrometry to characterize the distribution of PC species in cultured neurons of superior cervical ganglia. Inhibitors of actin dynamics (cytochalasin D and phallacidin) disrupted this gradient This is the first report of the gradual distribution of AA-PC along the axon and its association with actin dynamics. To visualize intrinsic neuronal PC at an intracellular level, we employed MALDI-imaging, wherein PC molecules can be detected with less fragmentation. AA-PC exhibited a gradient of increasing intensity along the proximodistal axonal axis This characteristic distribution of AA-PC was disrupted by the inhibition of actin dynamics, indicating that the AA-PC distribution is dependent on actin dynamics

EXPERIMENTAL PROCEDURES

RESULTS

E LC-ESI

DISCUSSION