α2δ expression sets presynaptic calcium channel abundance and release probability.
Synaptic neurotransmitter release is driven by Ca(2+) influx through active zone voltage-gated calcium channels (VGCCs). Control of active zone VGCC abundance and function remains poorly understood. Here we show that a trafficking step probably sets synaptic VGCC levels in rats, because overexpression of the pore-forming α1(A) VGCC subunit fails to change synaptic VGCC abundance or function. α2δs are a family of glycosylphosphatidylinositol (GPI)-anchored VGCC-associated subunits that, in addition to being the target of the potent neuropathic analgesics gabapentin and pregabalin (α2δ-1 and α2δ-2), were also identified in a forward genetic screen for pain genes (α2δ-3). We show that these proteins confer powerful modulation of presynaptic function through two distinct molecular mechanisms. First, α2δ subunits set synaptic VGCC abundance, as predicted from their chaperone-like function when expressed in non-neuronal cells. Second, α2δs configure synaptic VGCCs to drive exocytosis through an extracellular metal ion-dependent adhesion site (MIDAS), a conserved set of amino acids within the predicted von Willebrand A domain of α2δ. Expression of α2δ with an intact MIDAS motif leads to an 80% increase in release probability, while simultaneously protecting exocytosis from blockade by an intracellular Ca(2+) chelator. α2δs harbouring MIDAS site mutations still drive synaptic accumulation of VGCCs; however, they no longer change release probability or sensitivity to intracellular Ca(2+) chelators. Our data reveal dual functionality of these clinically important VGCC subunits, allowing synapses to make more efficient use of Ca(2+) entry to drive neurotransmitter release.
Department of Biochemistry, Weill Cornell Medical College, New York, New York 10023, USA.
Michael B
MB
Hoppa
Beatrice
B
Lana
Wojciech
W
Margas
Annette C
AC
Dolphin
Timothy A
TA
Ryan
D000200:Action Potentials; D000818:Animals; D015220:Calcium Channels / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism*; D020746:Calcium Channels, L-Type; D020013:Calcium Signaling; D005089:Exocytosis; D051379:Mice; D018377:Neurotransmitter Agents / Q000378:metabolism*; D017729:Presynaptic Terminals / Q000378:metabolism*; D011336:Probability; D051381:Rats
C486060:Cacna2d1 protein, rat; C486058:Cacna2d2 protein, mouse; C478375:Cacna2d3 protein, rat; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D018377:Neurotransmitter Agents