Just an FYI, with our install of WP 4.5x as of May 1, 2016, using this works fine for changing slug, but breaks the media element on the main WP admin menu.
You may prefer to simply use a function:
add_action('init', 'cng_author_base');
function cng_author_base() {
global $wp_rewrite;
$author_slug = 'profile'; // change slug name
$wp_rewrite->author_base = $author_slug;
}