Oh, forgot we're in a CMS. If /investor/ (or is it /investors/ ?) isn't a real, physical folder then neither the final slash nor the /index.php makes a difference. Redirect only the URL that was formerly used.
directories and folders
directory = folder. Same word in different languages.
But now wait a minute. RewriteRule ^investors/(.*)$ /aboutus/companyprofile? [R=301,L] If the part in parentheses can be empty (length 0) and you're not reusing it in the target, what's it even there for? All you need is ^investors/ with no closing anchor.