Uncoupling of Calcium Channel α1 and β Subunits in Developing Neurons

Abstract

Calcium channel ␤ subunits are key modulators of calcium channel function and membrane targeting of the pore-forming ␣ 1 subunit. Here we show that an invertebrate (Lymnaea stagnalis) homolog of P/Q-and Ntype calcium channels (LCa v 2), although colocalized with ␤ subunits in synapses of mature neurons, is physically uncoupled from the ␤ subunits in the leading edge of growth cones of outgrowing neurons. Moreover, LCa v 2 channels that mediate transmitter release in mature synapses also participate in neuronal outgrowth in growth cones. The differential association of ␤ subunits with synaptic calcium channels and those expressed in emergent neuronal growth suggests that ␤ subunits may play a role in the transformation of Ca v 2 calcium channel function in immature neurons and mature synapses.

PKC-Induced Intracellular Trafficking of CaV2 Precedes Its Rapid Recruitment to the Plasma Membrane

“…Interestingly, Ca v ␤ and Ca V 2 ␣ subunits appear to be associated with different cytoskeletal elements in immature growth cones (Spafford et al, 2004). It is tempting to speculate that the association between ␣ and ␤ subunits is regulated by PKC and/or by changes in the association of these subunits with the cytoskeleton.…”

“…2 B). As a further test for specificity of this antibody, we transfected mammalian GripTite 293 MSR cells with the Lymnaea Ca V 2 channel (Spafford et al, 2003;Spafford et al, 2004), which differs from the Aplysia Ca V 2 channel in only 2 of the 18 aa of the sequence against which the antibody was generated [SEHYNQPEWHVQFLYITE (Lymnaea) vs SEHYNQPEWFVDFLYITE (Aplysia)]. Cells were also transfected with the full-length Lymnaea Ca V 1 channel (Spafford et al, 2006).…”

“…Work with Lymnaea neurons has demonstrated that Ca V 2 subunits are associated with their ␤ subunits at mature release sites, but that the ␣ and ␤ subunits are uncoupled at the leading edge of growth cones of outgrowing neurites, and that ␤ subunit mRNA can be locally translated in growth cones (Spafford et al, 2004). Interestingly, Ca v ␤ and Ca V 2 ␣ subunits appear to be associated with different cytoskeletal elements in immature growth cones (Spafford et al, 2004).…”

“…It is tempting to speculate that the association between ␣ and ␤ subunits is regulated by PKC and/or by changes in the association of these subunits with the cytoskeleton. (Spafford et al, 2004).…”

G-proteins modulate invertebrate synaptic calcium channel (LCav2) differently from the classical voltage-dependent regulation of mammalian Cav2.1 and Cav2.2 channels

“…To study the characteristics of the LCa v 2 calcium channel, the wildtype LCa v 2 gene was cloned into pIRES2-EGFP vector from a previously modified LCa v 2 construct, dubbed 5ЈRatCa v 2.1-LCa v 2, in pMT2 plasmid, which bears an N-terminus from mammalian Ca v 2.1 (Spafford et al, 2003a;Spafford et al, 2004;Spafford et al, 2006). The wild-type channel was reconstructed with the Nterminus of wild-type LCa v 2 (GenBank Accession No.…”