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Synthetic antibody-derived immunopeptide provides neuroprotection in glaucoma through molecular interaction with retinal protein Histone H3.1

ABSTRACT: Glaucoma is a group of optic neuropathies characterized by the progressive degeneration of retinal ganglion cells (RGCs) as well as their axons leading to irreversible loss of sight. Medical management of the intraocular pressure (IOP) still represents the gold standard in glaucoma therapy, which only manages a risk factor and does not directly address the neurodegenerative component of this eye disease. Recently, our group showed that antibody derived immunopeptides (encoding complementarity-determining regions, CDRs) provide attractive glaucoma medication candidates and directly interfere its pathogenic mechanisms by different modes of action. In accordance with these findings, the present study showed the synthetic CDR2 peptide (INSDGSSTSYADSVK) significantly increased the RGCs viability in vitro in a concentration-dependent manner (p < 0.05 using a CDR2 concentration of 50 µg/mL). Employing state-of the-art immunoprecipitation experiments, we confirmed that synthetic CDR2 exhibited a high affinity towards the retinal target protein histone H3.1 (HIST1H3A) (p < 0.001 and log2 fold change > 3). Furthermore, virtual docking analyses predicted potential CDR2-specific binding regions of HIST1H3A, which might represent essential PTM sites for epigenetic regulations. Quantitative MS analysis revealed that 39 proteins were significantly changed between CDR2-treated and untreated control retinae (p < 0.05). An up-regulation of proteins involved in the energy production (e.g., ATP5F1B and MT-CO2) as well as the regulatory ubiquitin proteasome system (e.g., PSMC5) was induced by the synthetic CDR2 peptide. On the other hand, metabolic key enzymes (e.g., DDAH1 and MAOB) as well as ER stress-related proteins (e.g., SEC22B and VCP) were found with low abundancy in CDR2-treated retinae and were also partially confirmed by microarray technology. Based on these findings, it can be hypothesized that the specific protein-peptide interaction influences the regulatory epigenetic function of HIST1H3A promoting the neuroprotective mechanism on RGCs in vitro. It also might serve as basis for a synergistic immunotherapy of glaucoma in the future.

INSTRUMENT(S): LTQ Orbitrap

ORGANISM(S): Homo Sapiens (human) Sus Scrofa Domesticus (domestic Pig)

TISSUE(S): Brain, Macrophage

DISEASE(S): Wounds And Injuries

SUBMITTER: Carsten Schmelter

LAB HEAD: Prof. Dr. Dr. FH Grus

PROVIDER: PXD034046 | Pride | 2022-11-09

REPOSITORIES: Pride

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Synthetic antibody-derived immunopeptide provides neuroprotection in glaucoma through molecular interaction with retinal protein histone H3.1.

Fomo Kristian Nzogang KN Schmelter Carsten C Atta Joshua J Beutgen Vanessa M VM Schwarz Rebecca R Perumal Natarajan N Govind Gokul G Speck Thomas T Pfeiffer Norbert N Grus Franz H FH

Frontiers in medicine 20221014

Glaucoma is a group of optic neuropathies characterized by the progressive degeneration of retinal ganglion cells (RGCs) as well as their axons leading to irreversible loss of sight. Medical management of the intraocular pressure (IOP) still represents the gold standard in glaucoma therapy, which only manages a single risk factor and does not directly address the neurodegenerative component of this eye disease. Recently, our group showed that antibody-derived immunopeptides (encoding complementa ...[more]

PMID: 36313990

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Project description:Glaucoma is a complex, multifactorial optic neuropathy mainly characterized by the progressive loss of retinal ganglion cells (RGCs) and their axons, resulting in a decline of visual function. The pathogenic molecular mechanism of glaucoma is still not well understood, and therapeutic strategies specifically addressing the neurodegenerative component of this ocular disease are urgently needed. Novel immunotherapeutics might overcome this problem by targeting specific molecular structures in the retina and providing direct neuroprotection via different modes of action. Within the scope of this research, the present study showed for the first time beneficial effects of the synthetic CDR1 peptide SCTGTSSDVGGYNYVSWYQ on the viability of RGCs ex vivo in a concentration-dependent manner compared to untreated control explants (CTRL, 50 µg/mL: p < 0.05 and 100 µg/mL: p < 0.001). Thereby, this specific peptide was identified first as a potential biomarker candidate in the serum of glaucoma patients and was significantly lower expressed in systemic IgG molecules compared to healthy control subjects. Furthermore, MS-based co-immunoprecipitation experiments confirmed the specific interaction of synthetic CDR1 with retinal acidic leucine-rich nuclear phosphoprotein 32A (ANP32A; p < 0.001 and log2 fold change > 3), which is a highly expressed protein in neurological tissues with multifactorial biological functions. In silico binding prediction analysis revealed the N-terminal leucine-rich repeat (LRR) domain of ANP32A as a significant binding site for synthetic CDR1, which was previously reported as an important docking site for protein-protein interactions (PPI). In accordance with these findings, quantitative proteomic analysis of the retinae ± CDR1 treatment resulted in the identification of 25 protein markers, which were significantly differentially distributed between both experimental groups (CTRL and CDR1, p < 0.05). Particularly, acetyl-CoA biosynthesis I-related enzymes (e.g., DLAT and PDHA1), as well as cytoskeleton-regulating proteins (e.g., MSN), were highly expressed by synthetic CDR1 treatment in the retina; on the contrary, direct ANP32A-interacting proteins (e.g., NME1 and PPP2R4), as well as neurodegenerative-related markers (e.g., CEND1), were identified with significant lower abundancy in the CDR1-treated retinae compared to CTRL. Furthermore, retinal protein phosphorylation and histone acetylation were also affected by synthetic CDR1, which are both partially controlled by ANP32A. In conclusion, the synthetic CDR1 peptide provides a great translational potential for the treatment of glaucoma in the future by eliciting its neuroprotective mechanism via specific interaction with ANP32A’s N terminal LRR domain.

			Action	DRS
	CDR2_Beads_2M_R1.RAW	Raw
	CDR2_Beads_2M_R2.RAW	Raw
	CDR2_Beads_2M_R3.RAW	Raw
	CDR2_Beads_R1.RAW	Raw
	CDR2_Beads_R2.RAW	Raw