export const LocalesModel = PropTypes.shape({
  defaultLocale: PropTypes.string.isRequired,
  supportedLanguages: PropTypes.arrayOf(PropTypes.string).isRequired,
  messages: MessageModel,
});

import { LocalesModel } from '...';

const Component = () => ...

Component.propTypes = {
   supportedLanguages: ???
}

Component.propTypes = {
   supportedLanguages: LocalesModel.supportedLanguages
}