custom membership provider and unity dependency injection

I have found a few questions similar to the one I'm posting but I'm not getting from them what I really need. I'm still struggling to implement my CustomMembershipProvider using Microsoft Unity DI.

Custom Membership:

public class CustomMembershipProviderService : MembershipProvider
    {
        private readonly IUserService _userService;

        public CustomMembershipProviderService(IUserService userService)
        {
            this._userService = userService;
        }

        public override string ApplicationName
        {
        ...

User Service:

public class UserService : IUserService
    {
        private readonly IUserRepository _repository;
        private readonly IUnitOfWork _unitOfWork;
        public UserService(IUserRepository repository, IUnitOfWork unitOfWork)
        {
            this._repository = repository;
            this._unitOfWork = unitOfWork;
        }
        ...

AccountController:

public class AccountController : Controller
{
     // next line is what I don't feel too sure about what to do?
     // shouldn't my controller constructor use an Interface as its property?

     private readonly CustomMembershipProviderService _customMembershipProviderService;

     public AccountController(CustomMembershipProviderService customMembershipProviderService)
     {
         this._customMembershipProviderService = customMembershipProviderService;
     }
     ...

How can I create an interface for my MembershipProvider class?

I've tried:

public interface ICustomMembershipProvider : MembershipProvider

but I don't think that works, so I'm stuck, and don't know how to implement the MembershipProvider using my repositories, UoW, services, and Unity DI