Abstract
BackgroundIn invertebrates, the medicinal leech is considered to be an interesting and appropriate model to study neuroimmune mechanisms. Indeed, this non-vertebrate animal can restore normal function of its central nervous system (CNS) after injury. Microglia accumulation at the damage site has been shown to be required for axon sprouting and for efficient regeneration. We characterized HmC1q as a novel chemotactic factor for leech microglial cell recruitment. In mammals, a C1q-binding protein (C1qBP alias gC1qR), which interacts with the globular head of C1q, has been reported to participate in C1q-mediated chemotaxis of blood immune cells. In this study, we evaluated the chemotactic activities of a recombinant form of HmC1q and its interaction with a newly characterized leech C1qBP that acts as its potential ligand.MethodsRecombinant HmC1q (rHmC1q) was produced in the yeast Pichia pastoris. Chemotaxis assays were performed to investigate rHmC1q-dependent microglia migration. The involvement of a C1qBP-related molecule in this chemotaxis mechanism was assessed by flow cytometry and with affinity purification experiments. The cellular localization of C1qBP mRNA and protein in leech was investigated using immunohistochemistry and in situ hybridization techniques.ResultsrHmC1q-stimulated microglia migrate in a dose-dependent manner. This rHmC1q-induced chemotaxis was reduced when cells were preincubated with either anti-HmC1q or anti-human C1qBP antibodies. A C1qBP-related molecule was characterized in leech microglia.ConclusionsA previous study showed that recruitment of microglia is observed after HmC1q release at the cut end of axons. Here, we demonstrate that rHmC1q-dependent chemotaxis might be driven via a HmC1q-binding protein located on the microglial cell surface. Taken together, these results highlight the importance of the interaction between C1q and C1qBP in microglial activation leading to nerve repair in the medicinal leech.
Highlights
In invertebrates, the medicinal leech is considered to be an interesting and appropriate model to study neuroimmune mechanisms
We demonstrate the chemotactic activity of the recombinant protein on leech microglial cells and we used Recombinant HmC1q (rHmC1q) to tightly explore its functions in the leech nervous system following trauma
No significant difference was detected between the recognition of rHmC1q in the transformed yeast supernatant and native HmC1q released in the conditioned medium (Figure 1A, positive clone vs control)
Summary
The medicinal leech is considered to be an interesting and appropriate model to study neuroimmune mechanisms. This non-vertebrate animal can restore normal function of its central nervous system (CNS) after injury. We evaluated the chemotactic activities of a recombinant form of HmC1q and its interaction with a newly characterized leech C1qBP that acts as its potential ligand. In healthy brain, resting microglial cells show a ramified morphology [2] Under pathophysiological conditions, they rapidly change their morphology and change to amoeboid activated microglia. They rapidly change their morphology and change to amoeboid activated microglia This activation is controlled by ‘on’ or ‘off’ signals [3]. C1q plays an important role in microglia regulation after nerve injury
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