A choshuv Rav (head of a kashrus organization) said the source for the chosson aufruf is that there was a gate in the Beis Hamikdash designated for chassanim. Is there any source which connects this gate of the Beis Hamikdash to the aufruf?
This idea is discussed in Taamei Haminhagim 939, based on Pirkei Drebbi Eliezer 17 (near the end): The chasanim had a special gate in the Beis Hamikdash and people would come to bless them and wish them well; After the destruction of the Beis Hamikdash, when this method of practicing chessed with the chosson was no longer possible, Chazal instituted that the chassanim would visit the shuls and batei midrashos and the people of the town would rejoice with him there.
The Taamei Haminhagim (ibid.) suggests that this evolved to include escorting the chosson to shul and calling him to the Torah for an aliyah.