Neuregulin 1

1HAE, 1HAF, 1HRE, 1HRF, 3U7U3084n/aENSG00000157168n/aQ02297Q7RTW3n/aNM_001160004NM_001160005NM_001160007NM_001160008NM_004495NM_013956NM_013957NM_013958NM_013959NM_013960NM_013962NM_013964NM_001322197NM_001322201NM_001322202NM_001322205NM_001322206NM_001322207n/aNP_001153476NP_001153477NP_001153479NP_001153480NP_001309126NP_001309130NP_001309131NP_001309134NP_001309135NP_001309136NP_004486NP_039250NP_039251NP_039252NP_039253NP_039254NP_039256NP_039258NP_039251.2NP_001153471.1NP_001309130.1n/aNeuregulin 1 or NRG1 is a cell adhesion molecule that in humans is encoded by the NRG1 gene. NRG1 is one of four proteins in the neuregulin family that act on the EGFR family of receptors. Neuregulin 1 is produced in numerous isoforms by alternative splicing, which allows it to perform a wide variety of functions. It is essential for the normal development of the nervous system and the heart.1hae: HEREGULIN-ALPHA EPIDERMAL GROWTH FACTOR-LIKE DOMAIN, NMR, 20 STRUCTURES1haf: HEREGULIN-ALPHA EPIDERMAL GROWTH FACTOR-LIKE DOMAIN, NMR, MINIMIZED AVERAGE STRUCTURE1hre: SOLUTION STRUCTURE OF THE EPIDERMAL GROWTH FACTOR-LIKE DOMAIN OF HEREGULIN-ALPHA, A LIGAND FOR P180ERB41hrf: SOLUTION STRUCTURE OF THE EPIDERMAL GROWTH FACTOR-LIKE DOMAIN OF HEREGULIN-ALPHA, A LIGAND FOR P180ERB4 Neuregulin 1 or NRG1 is a cell adhesion molecule that in humans is encoded by the NRG1 gene. NRG1 is one of four proteins in the neuregulin family that act on the EGFR family of receptors. Neuregulin 1 is produced in numerous isoforms by alternative splicing, which allows it to perform a wide variety of functions. It is essential for the normal development of the nervous system and the heart. Neuregulin 1 (NRG1) was originally identified as a 44-kD glycoprotein that interacts with the NEU/ERBB2 receptor tyrosine kinase to increase its phosphorylation on tyrosine residues. It is known that an extraordinary variety of different isoforms are produced from the NRG1 gene by alternative splicing. These isoforms include heregulins (HRGs), glial growth factors (GGFs) and sensory and motor neuron-derived factor (SMDF). They are tissue-specific and differ significantly in their structure. The HRG isoforms all contain immunoglobulin (Ig) and epidermal growth factor-like (EGF-like) domains. GGF and GGF2 isoforms contain a kringle-like sequence plus Ig and EGF-like domains; and the SMDF isoform shares only the EGF-like domain with other isoforms. The receptors for all NRG1 isoforms are the ERBB family of tyrosine kinase transmembrane receptors. Through their displayed interaction with ERBB receptors, NRG1 isoforms induce the growth and differentiation of epithelial, neuronal, glial, and other types of cells. Neuregulin 1 is thought to play a role in synaptic plasticity. It has been shown that a loss of Neuregulin 1 within cortical projection neurons results in increased inhibitory connections and reduced synaptic plasticity. Similarly, overexpression of Neuregulin 1 results in disrupted excitatory-inhibitory connections, reduced synaptic plasticity, and abnormal dendritic spine growth. Mutations in human L1 cell adhesion molecules are reported to cause a number of neuronal disorders. In addition, recent research in Drosophila model has also shown Nrg's involvement in regulating dendritic pruning in ddaC neurons in a Rab5/ESCRT-mediated endocytic pathway. Thus, careful regulation of the amount of Neuregulin 1 must be maintained in order to preserve an intricate balance between excitatory and inhibitory connections within the central nervous system (CNS). Any disruption in this inhibitory system may contribute to impaired synaptic plasticity, a symptom endemic in schizophrenic patients. At least six major types (different N termini) of neuregulin 1 are known. Six types exist in humans and rodents (type I, II and III NRG1 are expressed in excitatory and inhibitory neurons, as well as astrocytes), and some types (I and IV) can be regulated by neuronal activity. Neuregulin 1-ErbB4 interactions are thought to play a role in the pathological mechanism of schizophrenia. A high-risk deCODE (Icelandic) haplotype was discovered in 2002 on the 5'-end of the gene. The SNP8NRG243177 allele from this haplotype was associated in 2006 with a heightened expression of the Type IV NRG1 in the brains of people suffering from schizophrenia. Further, the NRG1-ErbB4 signalling complex has been highlighted as a potential target for new antipsychotic treatment. Additionally, Neuregulin 1 has been shown to modulate anxiety-like behaviors. Endogenous Neuregulin 1 may bind to its receptor, ErbB4, expressed on GABAergic neurons within the basolateral amygdala. Administration of exogenous Neuregulin 1 to the basolateral amygdala of anxious mice produced an anxiolytic effect, which has been attributed to the enhancement of GABAergic neurotransmission. Thus, treatments aimed at reducing anxiety, which may contribute to emotional instability in many schizophrenic patients, by targeting the effects of mutations in NRG1 and ERBB4, may yield positive results for those afflicted by both anxiety disorders as well as schizophrenia. Neuregulin has been shown to be involved in the myelination of central nervous system (CNS) axons. There exist at least two modes of myelination within the CNS—one that is independent of neuronal activity and another that is promoted by the activation of NMDA receptors by glutamate on oligodendrocytes. Neuregulin is involved in the 'switching' of oligodendrocytes from the mode of myelination that is independent of neuronal activity to the mode that is dependent upon glutamate binding to NMDA receptors. It is thought that Neuregulin 1 found on axons of CNS neurons interacts with its receptor, ErbB4, to promote the myelination of that axon, and any disruption in this signaling contributes to decreased myelination. Since Neuregulin 1 promotes myelination and is decreased in schizophrenic patients, along with the finding that schizophrenic patients experience white matter deficits, mutations within Neuregulin 1 may underlie cognitive deficits associated with lower white matter integrity, especially within frontotemporal connections. The protein also has the putative ability to protect the brain from damage induced by stroke. Those with a genetic variant of neuregulin 1 tended to be more creative. There is evidence that NRG1 is a tumor suppressor gene.