The Matrix Proteins Hasp and Hig Exhibit Segregated Distribution within Synaptic Clefts and Play Distinct Roles in Synaptogenesis

Abstract

The synaptic cleft is the space through which neurotransmitters convey neural information between two synaptic terminals. This space is presumably filled with extracellular matrix molecules involved in synaptic function or differentiation. However, little is known about the identities of the matrix components, and it remains unclear how these molecules organize the matrix in synaptic clefts. In this study, we identified Hasp, a Drosophila secretory protein containing CCP and WAP domains. Molecular genetic analysis revealed that Hasp diffuses extracellularly and is predominantly captured at synaptic clefts of cholinergic synapses. Furthermore, Hasp regulates levels of DLG and the nAChR subunits D␣6 and D␣7 at postsynaptic terminals. Hasp is required for trapping of another matrix protein, Hig, which is also secreted and diffused in the brain, at synaptic clefts of cholinergic synapses; however, Hig is dispensable for localization of Hasp at synaptic clefts. In addition, in the brains of triple mutants for the nAChR subunits D␣5, D␣6, and D␣7, the level of Hig, but not Hasp, was markedly reduced in synaptic regions, indicating that these nAChR subunits are required to anchor Hig to synaptic clefts. Highresolution microscopy revealed that Hasp and Hig exhibit segregated distribution within individual synaptic clefts, reflecting their differing roles in synaptogenesis. These data provide insight into how Hasp and Hig construct the synaptic cleft matrix and regulate the differentiation of cholinergic synapses, and also illuminate a previously unidentified architecture within synaptic clefts.

Cellular diversity in the Drosophila midbrain revealed by single-cell transcriptomics

“…In addition to known markers of monoaminergic neuronal types, we found new genes expressed in these populations ( Figure 7C ), that are likely to have an important role for their development and connectivity, such as kekkon 1 ( kek1 ) in dopaminergic neurons (DANs) ( Ghiglione et al, 1999 ), or IGF-II mRNA-binding protein ( Imp ) and Jim Lovell ( lov ) in serotonergic neurons ( Bjorum et al, 2013 ; Geng and Macdonald, 2006 ; Munro et al, 2006 ). High expression in TA neurons of hikaru genki ( hig ), which encodes a protein generally found in the synaptic clefts of cholinergic synapses ( Nakayama et al, 2014 ; 2016 ), may highlight the importance of cholinergic input to these neurons.…”

A Drosophila model for developmental nicotine exposure

“…Larva and adult expression are primarily detected in the central nervous system [30–33]. Expression at the mushroom body calyces has been confirmed by other groups [34–36], including expression at the calyces of larval mushroom bodies [35]. The mushroom bodies in turn have been implicated in ethanol reward, and ethanol-induced hyperactivity [37,38].…”

A Neuron-Specific Antiviral Mechanism Modulates the Persistent Infection of Rice Rhabdoviruses in Leafhopper Vectors

“…The CCP domains of Hig proteins are evolutionarily conserved, play important roles in neuron development, and interact with the surface of several pathogenic viruses (Casasnovas et al, 1999;Xiao et al, 2014Xiao et al, , 2015Nakayama et al, 2016). For example, the CCP domains of Hig homolog of A. aegypti interact with the surface of flaviviruses and effectively restrict flavivirus infection in the CNS of mosquitoes, preventing the lethal flaviviral infection of mosquitoes (Xiao et al, 2014(Xiao et al, , 2015.…”

“…The predicted amino acid sequence (636 aa) of NcHig was analyzed and contained one putative immunoglobulin (IG) domain and five putative CCP domains ( Figure 1A). The CCP domains are the signature features of many mammalian and insect complement proteins and can recognize pathogenic microorganisms (Xiao et al, 2014(Xiao et al, , 2015Nakayama et al, 2016).…”