Courteney Cox and Renee Zellweger were among the celebrities supporting Hollywood publicist Nanci Ryder at an ALS walk in Los Angeles.

Nanci was diagnosed with amyotrophic lateral sclerosis (ALS) in 2014, and the neurodegenerative disease has taken her ability to speak and left her largely immobile.

A number of Nanci's friends, led by Courteney and Renee, participated in the walk in the annual fundraiser walk.

Former 'Friends' star Courteney admits that she finds it difficult not being able to communicate with Nanci but it ''means the world'' when she gets a smile.

Speaking to PEOPLE, the 55-year-old actress said: ''It's hard to get a smile and it means the world. It's not fair to place something on a smile, but when you do get a smile from Nanci, it's the best feeling in the world.

''It's hard because the communication isn't what it used to be. When she was first diagnosed I was kind of able - she would let me in on the highs and lows and the emotions and where she was. And now it's harder to communicate and it's sad.''

'Judy' actress Renee, 50, continues to be impressed by Nanci's spirit, even though her condition has worsened.

She said: ''Her disease has progressed, and she hasn't spoken in about almost four years. It's just run its course as it does, but she's levelled out and hanging in there, and her joy for life remains the same. Any time something new shows up that seems insurmountably difficult, she moves the goalpost.''

Renee also revealed that she hopes to organise a private screening of her new Judy Garland biopic 'Judy' for Nanci.

She explained: ''I was hoping she would come to the premiere, but it's just logistics are a little challenging, and she would get a little tired from all the noise and the people and everything. So I'll get her a screener and she'll have it.''