Passing an expression tree as a parameter to another expression tree

I have two expression trees defined like this:

private Expression<Func<TEntity, TPropertyResult>> PropertyAccessor { get; set; }

and

private Expression<Func<TPropertyResult, bool>> TestExpression { get; set; }

I need to create a new expression tree that will result in the equivalent of:

var expression = p => this.TestExpression(this.PropertyAccessor(p));

When using Expression.Invoke(this.TestExpression, this.PropertyAccessor), I get the following error

{"Expression of type 'System.Func`2[MyEntity,System.String]' cannot be used for parameter of type 'System.String'"}

TPropertyResult is a string during my test.

I tried using Expression.Call or Expression.Invoke. No luck. What should I use?