Identification and characterization of two orphan proteins as novel cis-ligands of neurexin complexes
Abstract/Contents
- Abstract
- Synapses are the basic units of information processing in the central nervous system (CNS). Synaptic properties are controlled by trans-synaptic adhesion complexes. Neurexins are central components of these complexes and organize both pre- and postsynaptic machinery by binding to a multitude of diverse ligands. However, known neurexin ligands seem to account for only a fraction of neurexin interactions, and identifying and validating novel neurexin ligands remain a challenge. In collaboration with the Fakler laboratory, we performed a proteomic screen for endogenous neurexin ligands enabled, in part, by the generation of a mouse line in which an epitope tag is knocked in to an extracellular region of neurexin 1. Members of two brain-enriched orphan protein families were detected in neurexin complexes immunoisolated from mouse brains: (1) FAM19A1 and FAM19A2, part of the FAM19A/TAFA family; and (2) TMEM178B, a close homologue of TMEM178A. Using protein chemistry and cell biological approaches, we identified FAM19A1-A4 as neuron subtype-specific, activity-regulated proteins that form covalent complexes with neurexins within the secretory pathway via the neurexin cysteine loop. To the best of our knowledge, this is a structurally unprecedented interaction mode that differs from that of other neurexin ligands. Further, FAM19A1-A4 regulate neurexin post-translational modifications, thus shaping neurexin ligand interactions and synapse properties. In a separate series of experiments utilizing mouse genetics, we found that Tmem178a and Tmem178b are necessary for mouse survival and that the Tmem178b deletion results in lower body weights and abnormal behaviors suggestive of brain dysfunction, though no striking changes in synapses were detected. Interestingly, we found that these predicted tetraspanin proteins are endogenously cleaved and the cleavage fragments remain covalently bound at the surface of axons in hippocampal cultures. In summary, our studies deorphanize FAM19A1-A4 and, putatively, TMEM178B as novel, brain-enriched members of the vertebrate neurexin interactome, thus expanding our understanding of synaptic components and laying a foundation for future functional studies. More broadly, the study of vertebrate-specific CNS-enriched orphan proteins will inform our understanding of vertebrate CNS molecular and cellular diversity and complexity and thus shed light on vertebrate-specific CNS functions and adaptations.
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource. |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2021; ©2021 |
| Publication date | 2021; 2021 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Khalaj, Anna Jeanne |
|---|---|
| Degree supervisor | Südhof, Thomas C |
| Thesis advisor | Südhof, Thomas C |
| Thesis advisor | Brünger, Axel T |
| Thesis advisor | Chen, Lu, (Professor of neurosurgery) |
| Thesis advisor | Luo, Liqun, 1966- |
| Degree committee member | Brünger, Axel T |
| Degree committee member | Chen, Lu, (Professor of neurosurgery) |
| Degree committee member | Luo, Liqun, 1966- |
| Associated with | Stanford University, Neurosciences Program |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Anna Jeanne Khalaj. |
|---|---|
| Note | Submitted to the Neurosciences Program. |
| Thesis | Thesis Ph.D. Stanford University 2021. |
| Location | https://purl.stanford.edu/cp200pt0640 |
Access conditions
- Copyright
- © 2021 by Anna Jeanne Khalaj
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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