Two classes of matrix metalloproteinases reciprocally regulate synaptogenesis

Abstract

Synaptogenesis requires orchestrated intercellular communication between synaptic partners, with trans-synaptic signals necessarily traversing the extracellular synaptomatrix separating presynaptic and postsynaptic cells. Extracellular matrix metalloproteinases (Mmps) regulated by secreted tissue inhibitors of metalloproteinases (Timps), cleave secreted and membrane-associated targets to sculpt the extracellular environment and modulate intercellular signaling. Here, we test the roles of Mmp at the neuromuscular junction (NMJ) model synapse in the reductionist Drosophila system, which contains just two Mmps (secreted Mmp1 and GPI-anchored Mmp2) and one secreted Timp. We found that all three matrix metalloproteome components co-dependently localize in the synaptomatrix and show that both Mmp1 and Mmp2 independently restrict synapse morphogenesis and functional differentiation. Surprisingly, either dual knockdown or simultaneous inhibition of the two Mmp classes together restores normal synapse development, identifying a reciprocal suppression mechanism. The two Mmp classes coregulate a Wnt trans-synaptic signaling pathway modulating structural and functional synaptogenesis, including the GPIanchored heparan sulfate proteoglycan (HSPG) Wnt co-receptor Dally-like protein (Dlp), cognate receptor Frizzled-2 (Frz2) and Wingless (Wg) ligand. Loss of either Mmp1 or Mmp2 reciprocally misregulates Dlp at the synapse, with normal signaling restored by coremoval of both Mmp classes. Correcting Wnt co-receptor Dlp levels in both Mmp mutants prevents structural and functional synaptogenic defects. Taken together, these results identify an Mmp mechanism that fine-tunes HSPG co-receptor function to modulate Wnt signaling to coordinate synapse structural and functional development.

Diverse roles for glycosaminoglycans in neural patterning

“…4) (Endo et al, 2003;Wang and Page-McCaw, 2014). Mutations in two metalloproteinases (Mmps) caused the localization of glypican to be more restricted (Mmp1) or broader (Mmp2) at the NMJ (Dear et al, 2016). The defects in synapse formation and function in Mmp1 mutants (more restricted expression of glypican) or Mmp2 mutants (broader expression) could be rescued by overexpression of ectopic glypican or removing a copy of glypican, respectively (Dear et al, 2016).…”

The HSPG Glypican Regulates Experience-Dependent Synaptic and Behavioral Plasticity by Modulating the Non-Canonical BMP Pathway

“…It remains unclear how octopamine signaling at type I synaptic regions regulates postsynaptic Dlp levels. Broadie and collaborators revealed that ECM metalloproteinases (Mmp1 and Mmp2) and the tissue inhibitor of metalloproteinases (Timp) play critical roles in synapse formation and activity-dependent plasticity in the Drosophila NMJ (Dear et al, 2016(Dear et al, , 2017Shilts and Broadie, 2017). Mmp2 from the presynaptic and postsynaptic compartments has been shown to negatively regulate synaptic Dlp levels at the NMJ, possibly by the proteolytic cleavage of Dlp core proteins (Wang and Page-McCaw, 2014).…”

“…Mmp2 from the presynaptic and postsynaptic compartments has been shown to negatively regulate synaptic Dlp levels at the NMJ, possibly by the proteolytic cleavage of Dlp core proteins (Wang and Page-McCaw, 2014). However, Mmp1 is known to associate with Dlp via heparan sulfate (HS) chains and positively regulate Dlp expression levels at type I endings (Dear et al, 2016). Octopamine signaling after food deprivation may activate the proteolytic activity of Mmp2 at type I synaptic regions, leading to a decrease in postsynaptic Dlp levels.…”

“…Recent studies revealed that many synapses in the mammalian brain are wrapped with a proteoglycan-rich extracellular matrix (ECM) that plays important roles in experience-dependent synaptic plasticity (Maeda et al, 2010;Miyata and Kitagawa, 2017). The type I synaptic boutons of Drosophila NMJs are also surrounded by a rich ECM containing the heparan sulfate proteoglycans (HSPGs) perlecan (Trol), syndecan (Sdc), and glypican (Dally-like, Dlp) (Johnson et al, 2006;Dani et al, 2012;Kamimura et al, 2013;Dear et al, 2016;Nguyen et al, 2016). These HSPGs play critical roles in NMJ development by regulating Wnt/Wingless (Wg), a bone morphogenetic protein (BMP) ligand, glass bottom boat (Gbb), and the receptor protein tyrosine phosphatase LAR.…”

Wingless promotes JNK/MMPs positive feedback loop mediate tumour microtubes expansion, glioma progression and neurodegeneration

“…Antibodies used were: mouse anti-Wg (DSHB 1:50), mouse anti-Repo (DSHB 1:50), mouse anti-Fz1 (DSHB 1:50), mouse anti-Cyt-Arm (DSHB 1:50), mouse anti-MMP1 (DSHB 5H7B11, 3A6B4, 3B8D12, 1:50), rabbit anti-MMP2 (1:500, K. Broadie) [85], guinea pig anti-grnd (1:250, P. Leopold) [75], mouse anti-β-galactosidase (Sigma, 1:500), rabbit anti-GFP (Invitrogen A11122, 1:500), mouse anti-GFP (Invitrogen A11120,…”