Proteome modifications of the medicinal leech nervous system under bacterial challenge

Abstract

Once considered as lacking intrinsic immune mechanisms, the CNS of vertebrates is now known to be capable of mounting its own innate immune response. Interestingly, while invertebrates have been very useful in the interpretation of general vertebrate innate immunity mechanisms, only scarce data are available on the immune response of nervous tissue within this group. This study provides new data on the innate immune response of medicinal leech Hirudo medicinalis CNS. We identified several spots in 2-D gels of leech CNS proteins that showed specific changes following bacterial challenge, thus demonstrating the ability of the leech nervous system to mount a response to an immune stress. Protein identifications were based on comparison of sequence data with publicly available databases and a recently established leech ESTs database. The broad nature of the identified proteins suggests a clear involvement of cytoskeletal rearrangements, endoplasmic reticulum stress, modulation of synaptic activity and calcium mobilization, all during the first 24 hours of this response. Moreover, several of these proteins are specifically expressed in glial cells, suggesting an important role for glial cells in the immune response of the leech nervous system, similar to what has been observed in vertebrates.

Multiple Changes in Peptide and Lipid Expression Associated with Regeneration in the Nervous System of the Medicinal Leech

“…These results are consistent with the data obtained by the bottom-up approach, supporting the tentative conclusion that gliarin and antimicrobial-neurotrophic factors are implicated in the adult nerve cord regeneration. In addition, our observations complement those obtained by genomic and 2D-Gel proteomic studies [3], [5], [7], [9] ( Table 3 ). By comparison, Blackshaw and collaborators have reported, in studies using subtractive cDNAs library from regenerating and non-regenerating central ganglia, the presence of leech homologues of mammalian genes with established functions, including the cytoskeletal proteins actin, tubulin and Protein 4.1, ATP synthase, the neuron-specific protein synapsin, Cysteine Rich Intestinal Protein (CRIP), myohemerythrin and a novel protein ReN3, exclusively expressed in invertebrates [3], [4], [21], [22].…”

“…Similarly on-going proteomic studies of the leech CNS performed by our group have shown that some molecules detected by transcriptomic approaches, e.g. cytoskeletal and metabolic proteins, foldases, calcium sensors, kinases and neurohemerythrin (reflecting specific cytoskeletal rearrangements linked to cell migration), vesicular trafficking as well as the modulation of synaptic activity, are also observed in excised adult ganglia challenged by bacterial toxins [7], [9].…”

“…Similar to Hm -ABP3, the gliarin fragment and the neurohemerythrin isoforms appeared to become more abundant throughout the period examined, suggesting that their roles might become more important as the process of regeneration is established, but might not be as significant immediately after the lesion is made, when the neuroinflammatory response occurs [11]–[14], [19], [20]. Curiously, the two neurohemerytrin isoforms are differentially regulated, possibly reflecting different functions [7], [9]. These results are consistent with the data obtained by the bottom-up approach, supporting the tentative conclusion that gliarin and antimicrobial-neurotrophic factors are implicated in the adult nerve cord regeneration.…”

“…The remaining three peaks also correspond to previously identified leech proteins. Peak 4 ( Figure 4 ) represents a peptide sequence related to the intermediate filament gliarin [9], while Peaks 5 and 6 are both related to neurohemerythrin [7]. Neither antimicrobial nor neurotrophic activities were detected for any of these three molecules (data not shown).…”

“…Interestingly, several molecules detected in the differential transcription studies mentioned above have also been identified in recent proteomic studies of excised leech CNS challenged with bacterial toxins. These include cytoskeletal and metabolic proteins, foldases, calcium sensors, kinases and neurohemerythrin [9]. While this is a comparison of two levels of analysis - transcriptomic and proteomic - and responses to two different types of stress - mechanical trauma and septic shock - it is nonetheless satisfying that there is a convergence of results.…”