Neither commonly used Scrabble dictionaries recognize AKA as a word. However, I have read recently that some of the scrabble copycat games may be allowing use of selected acronyms.
No. Excelsis is not an acceptable Scrabble word.
No. Viz is not an acceptable Scrabble word.
No. Cie is not an acceptable Scrabble word.
Abbreviations are not acceptable in Scrabble.
No. Eariest is not an acceptable Scrabble word.
No. Wop is not an acceptable Scrabble word.
No. Fo is not an acceptable Scrabble word.
Yes. Jo is an acceptable Scrabble word.
Yes. Re is an acceptable Scrabble word.
Yes, "nus" is an acceptable word in Scrabble.
Yes. Moot is an acceptable Scrabble word.
In my eyes yes RN is an acceptable scrabble word.