Dataset Information

Identification of a truncated ?1-chimaerin variant that inactivates nuclear Rac1.

ABSTRACT: ?1-chimaerin belongs to the chimaerin family of GTPase-activating proteins (GAPs) and is encoded by the CHN2 gene, which also encodes the ?2- and ?3-chimaerin isoforms. All chimaerin isoforms have a C1 domain that binds diacylglycerol as well as tumor-promoting phorbol esters and a catalytic GAP domain that inactivates the small GTPase Rac. Nuclear Rac has emerged as a key regulator of various cell functions, including cell division, and has a pathological role by promoting tumorigenesis and metastasis. However, how nuclear Rac is regulated has not been fully addressed. Here, using several approaches, including siRNA-mediated gene silencing, confocal microscopy, and subcellular fractionation, we identified a nuclear variant of ?1-chimaerin, ?1-?7p-chimaerin, that participates in the regulation of nuclear Rac1. We show that ?1-?7p-chimaerin is a truncated variant generated by alternative splicing at a cryptic splice site in exon 7. We found that, unlike other chimaerin isoforms, ?1-?7p-chimaerin lacks a functional C1 domain and is not regulated by diacylglycerol. We found that ?1-?7p-chimaerin localizes to the nucleus via a nuclear localization signal in its N terminus. We also identified a key nuclear export signal in ?1-chimaerin that is absent in ?1-?7p-chimaerin, causing nuclear retention of this truncated variant. Functionally analyses revealed that ?1-?7p-chimaerin inactivates nuclear Rac and negatively regulates the cell cycle. Our results provide important insights into the diversity of chimaerin Rac-GAP regulation and function and highlight a potential mechanism of nuclear Rac inactivation that may play significant roles in pathologies such as cancer.

SUBMITTER: Casado-Medrano V

PROVIDER: S-EPMC6996883 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Identification of a truncated β1-chimaerin variant that inactivates nuclear Rac1.

Casado-Medrano Victoria V Barrio-Real Laura L Gutiérrez-Miranda Laura L González-Sarmiento Rogelio R Velasco Eladio A EA Kazanietz Marcelo G MG Caloca María J MJ

The Journal of biological chemistry 20191222 5

β1-chimaerin belongs to the chimaerin family of GTPase-activating proteins (GAPs) and is encoded by the <i>CHN2</i> gene, which also encodes the β2- and β3-chimaerin isoforms. All chimaerin isoforms have a C1 domain that binds diacylglycerol as well as tumor-promoting phorbol esters and a catalytic GAP domain that inactivates the small GTPase Rac. Nuclear Rac has emerged as a key regulator of various cell functions, including cell division, and has a pathological role by promoting tumorigenesis ...[more]

PMID: 31871052

Similar Datasets

Project description:BackgroundDevelopmental and epileptic encephalopathies (DEEs) signify a group of heterogeneous neurodevelopmental disorder associated with early-onset seizures accompanied by developmental delay, hypotonia, mild to severe intellectual disability, and developmental regression. Variants in the DNM1 gene have been associated with autosomal dominant DEE type 31A and autosomal recessive DEE type 31B.MethodsIn the current study, a consanguineous Pakistani family consisting of a proband (IV-2) was clinically evaluated and genetically analyzed manifesting in severe neurodevelopmental phenotypes. WES followed by Sanger sequencing was performed to identify the disease-causing variant. Furthermore, 3D protein modeling and dynamic simulation of wild-type and mutant proteins along with reverse transcriptase (RT)-based mRNA expression were checked using standard methods.ResultsData analysis of WES revealed a novel homozygous non-sense variant (c.1402G>T; p. Glu468*) in exon 11 of the DNM1 gene that was predicted as pathogenic class I. Variants in the DNM1 gene have been associated with DEE types 31A and B. Different bioinformatics prediction tools and American College of Medical Genetics guidelines were used to verify the identified variant. Sanger sequencing was used to validate the disease-causing variant. Our approach validated the pathogenesis of the variant as a cause of heterogeneous neurodevelopmental disorders. In addition, 3D protein modeling showed that the mutant protein would lose most of the amino acids and might not perform the proper function if the surveillance non-sense-mediated decay mechanism was skipped. Molecular dynamics analysis showed varied trajectories of wild-type and mutant DNM1 proteins in terms of root mean square deviation, root mean square fluctuation and radius of gyration. Similarly, RT-qPCR revealed a substantial reduction of the DNM1 gene in the index patient.ConclusionOur finding further confirms the association of homozygous, loss-of-function variants in DNM1 associated with DEE type 31B. The study expands the genotypic and phenotypic spectrum of pathogenic DNM1 variants related to DNM1-associated pathogenesis.

Dataset Information

Identification of a truncated ?1-chimaerin variant that inactivates nuclear Rac1.

Publications

Identification of a truncated β1-chimaerin variant that inactivates nuclear Rac1.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets