5h49
Crystal structure of Cbln1
Structural highlights
FunctionCBLN1_RAT Required for synapse integrity and synaptic plasticity. During cerebellar synapse formation, essential for the formation and maintenance of parallel fiber and Purkinje cell synapses. When parallel fibers make contact with Purkinje spines, CBLN1 interaction with GRID2 triggers the recruitment of NRXN1 and secretory vesicles to the sites of contact. NRXN1-CBLN1-GRID2 signaling induces presynaptic morphological changes, which may further accumulate pre- and postsynaptic components to promote bidirectional maturation of parallel fiber - Purkinje cell functionally active synapses by a positive feedback mechanism. Required for CBLN3 export from the endoplasmic reticulum and secretion (By similarity). The cerebellin exerts neuromodulatory functions. Directly stimulates norepinephrine release via the adenylate cyclase/PKA-dependent signaling pathway; and indirectly enhances adrenocortical secretion in vivo, through a paracrine mechanism involving medullary catecholamine release. A conversion to [des-Ser1]-cerebellin by endopeptidases seems to be required for its autocrine-paracrine regulatory functions.[1] [2] Publication Abstract from PubMedUnlike cerebellin 1 (Cbln1), which bridges neurexin (Nrxn) receptors and delta-type glutamate receptors in a trans-synaptic triad, Cbln4 was reported to have no or weak binding for the receptors despite sharing approximately 70% sequence identity with Cbln1. Here, we report crystal structures of the homotrimers of the C1q domain of Cbln1 and Cbln4 at 2.2 and 2.3 A resolution, respectively. Comparison of the structures suggests that the difference between Cbln1 and Cbln4 in GluD2 binding might be because of their sequence and structural divergence in loop CD. Surprisingly, we show that Cbln4 binds to Nrxn1beta and forms a stable complex with the laminin, nectin, sex-hormone binding globulin (LNS) domain of Nrxn1beta. Furthermore, the negative-stain electron microscopy reconstruction of hexameric full-length Cbln1 at 13 A resolution and that of the Cbln4/Nrxn1beta complex at 19 A resolution suggest that Nrxn1beta binds to the N-terminal region of Cbln4, probably through strand beta10 of the S4 insert. Cbln1 and Cbln4 Are Structurally Similar but Differ in GluD2 Binding Interactions.,Zhong C, Shen J, Zhang H, Li G, Shen S, Wang F, Hu K, Cao L, He Y, Ding J Cell Rep. 2017 Sep 5;20(10):2328-2340. doi: 10.1016/j.celrep.2017.08.031. PMID:28877468[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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