The presynaptic scaffolding protein Piccolo organizes the readily releasable pool at the calyx of Held

Abstract

Synaptic vesicles (SVs) are released at the active zone (AZ), a specialized region of the presynaptic plasma membrane organized by a highly interconnected network of multidomain proteins called the cytomatrix of the active zone (CAZ). Two core components of the CAZ are the large, highly homologous scaffolding proteins Bassoon and Piccolo, whose function is not well understood. To investigate their role in synaptic transmission, we established the small hairpin RNA (shRNA)-mediated in vivo knockdown (KD) of Bassoon and Piccolo at the rat calyx of Held synapse. KD of Bassoon and Piccolo, separately or simultaneously, did not affect basic SV release. However, short-term depression (STD) was prominently increased by the KD of Bassoon, whereas KD of Piccolo only had a minor effect. The observed alterations in STD were readily explained by reduced SV replenishment in synapses deficient in either of the proteins. Thus, the regulation of SV refilling during ongoing synaptic activity is a shared function of Bassoon and Piccolo, although Bassoon appears to be more efficient. Moreover, we observed the recruitment of slowly-releasing SVs of the readily-releasable pool (RRP), which are normally not available for action potential-induced release, during high-frequency stimulation in Piccolo-deficient calyces. Therefore, the results obtained in the present study suggest a novel and specific role for Piccolo in the organization of the subpools of the RRP.

Genes Involved in the Development and Physiology of Both the Peripheral and Central Auditory Systems

“…At the endbulb of Held synapse formed between spiral ganglion neurons and bushy cells of the anteroventral CN, bassoon and piccolo have additive roles in the replenishment of synaptic vesicles (Butola et al 2017). At calyx of Held terminals, piccolo or bassoon knockdown results in slowed synaptic vesicle replenishment in the active zone (Parthier et al 2018).…”

FMRP binding to a ranked subset of long genes is revealed by coupled CLIP and TRAP in specific neuronal cell types

“…In the presynaptic cerebellar granule neuron an important family of FMRP targets are those that make up the presynaptic cytoskeletal matrix including Piccolo (Pclo), Bassoon (Bsn) and Oboe (Rims2), a group of presynaptic proteins that orchestrate the cycling of synaptic vesicles in the active zone of the presynaptic cytoskeletal matrix 167,168 . Significantly, all three mRNAs are high confidence targets of FMRP in granule neurons ( Table 2).…”

A Multiple Piccolino-RIBEYE Interaction Supports Plate-Shaped Synaptic Ribbons in Retinal Neurons

“…One of the highly conserved AZ components is the large (Ͼ500 kDa) scaffold protein Piccolo, which organizes various aspects of presynaptic function at chemical synapses (Cases-Langhoff et al, 1996;Wang et al, 1999;Gundelfinger et al, 2016). Among these are functions in AZ assembly during synaptogenesis (Shapira et al, 2003), the dynamic regulation of presynaptic actin (Waites et al, 2011;Wagh et al, 2015), the control of presynaptic proteostasis (Waites et al, 2013;Ivanova et al, 2016), the regulation of activity-dependent communication between the presynapse and the nucleus (Ivanova et al, 2015), and the organization of the readily releasable pool of SVs (Butola et al, 2017;Parthier et al, 2018). Piccolo possesses regions of high sequence similarity to Bassoon, another conserved AZ protein.…”