McGee had been on administrative leave from UMKC since October 2.
"The university deserves a full-time assistant coach and I am not able to provide that to the basketball team while the false allegations against me are being investigated," McGee wrote in a letter to UMKC Director of Athletics Carla Wilson.
A statement from UMKC said the university would have no further comment on the matter while the investigation is ongoing.
Louisville is in the middle of a sex scandal that could tarnish its reputation and the integrity of its leaders, including head coach Rick Pitino.
Sex and stripper parties
ESPN's "Outside the Lines" reported this week that McGee paid for sex and stripper parties on the Louisville campus for basketball players and recruits, allegations made by a self-described escort named Katina Powell.
According to "Outside the Lines," five former University of Louisville basketball players and recruits said McGee paid for strippers to attend nearly two dozen parties at the dorm from 2010-2014. Each of the players and recruits attended different parties. At those parties, the ESPN report says, there were dancers who stripped naked. Of the five players interviewed by ESPN, three said they attended parties as recruits and again when they were players at Louisville. The ESPN report says one of the former players said he had sex with one of the strippers and that McGee paid her for it.
The allegations first were made public in a book published earlier this month by Powell and Dick Cady called "Breaking Cardinal Rules: Basketball and the Escort Queen."
Powell told ESPN she was paid $10,000 for supplying dancers from 2010 to 2014. She also said there were what she called "side deals," in which McGee allegedly gave her cash to pay women to have sex with Louisville players, recruits and guardians who accompanied recruits on visits.
Scott Cox, an attorney for McGee, said earlier this month that his client denies all of the allegations. Louisville and the NCAA are investigating the allegations, as is UMKC.
Did Pitino know?
Powell suggested Pitino had to know something about the situation.
"This is my theory," Powell said on "Outside the Lines." "Four years. A boatload of recruits. A boatload of dancers. Loud music. Alcohol. Security. Cameras. Basketball players who came in at will. You got players that are so loyal to Pitino. Who wouldn't be like, hey, you know, we got dancers and sex and all that going on? My thing is how could he not know?"
Pitino has repeatedly denied that he knew anything about the alleged on-campus parties inside Billy Minardi Hall, a dorm for athletes named after Pitino's late brother-in-law, who was killed in the 9/11 terror attack on the World Trade Center.
On Tuesday, Pitino told ESPN by phone that McGee "needs to come out and tell the truth."
"I don't know if any of this is true or not," Pitino told the sports network. "There's only one person who knows the truth, and he needs to come out and tell the truth to his teammates, to the University of Louisville, to his fans and to his coaches that have taught him to do the right thing for years and allowed him to be part of something special here.
"He's the only one with any answers. Whether it's true or not, I don't know. ... Everything else is absurd. I don't care about the legal issues. If he's done something wrong, he has to own up to it and do his penance."
Pitino: 'I will not resign'
Pitino followed up Thursday with a public letter to fans on his website -- above a preview of Louisville's upcoming season -- apologizing that "we all have to endure the pain of these allegations" and promising to remain on the job while "investigators do their job and we ... play basketball."
"I will not resign and let you down," Pitino wrote. "Someday, I will walk away in celebration of many memorable years but that time is not now.
"I do not fight these accusations but rather turn the other cheek. Couldn't do it at 33, but at 63 it's the wise thing to do."
McGee played for Louisville under Pitino from 2005-2009. He was on the Louisville coaching staff from 2010 to 2014, and took the job at UMKC later in 2014.
Who picked up the tab?
There have been questions about the source of any money allegedly paid.
According to Cox, McGee's attorney, his client "was not highly paid at all" at Louisville. His primary compensation, the attorney said, was a free room at Minardi Hall.
"He was just paid a relatively small stipend," Cox said.
"To suggest that he could pay multiple prostitutes to come to Minardi Hall and have sexual relations with athletes is ludicrous. He could never have afforded to do anything like that nor would he have done anything like that."
"I knew they weren't college girls," ESPN quoted an unnamed recruit as saying. "It was crazy. It was like I was in a strip club." ESPN said that recruit signed with another school.
Pitino said on October 2 that when the story broke, he "questioned everybody, if anybody even has a little knowledge or hearsay or seen anybody. And everybody to the person, 15 people, said they had no knowledge of anything, never seen anything."
College basketball powerhouse
Pitino's record on the basketball court has reached legendary status. He's the first coach in NCAA history to win a national championship at two schools (Kentucky and Louisville) and was the first to coach three schools (Providence, Kentucky and Louisville) to the NCAA Final Four. In his 30 seasons as a college basketball head coach, he has gone 722-254, a .740 winning percentage. At Louisville, where he's been since 2001, his record stands at 368-126. He's also been the head coach of the New York Knicks and Boston Celtics in the NBA.
Louisville athletic director Tom Jurich backs his coach.
"He has a long-term contract," Jurich said Tuesday through Louisville spokesman Kenny Klein. "He absolutely did not know anything about these allegations."