Making shared_ptr lose ownership of memory

I have a shared_ptr<MyProto> which I pass around. Eventually, in certain situations, I want pass the raw pointer to a function which then becomes the memory owner. In those cases the shared_ptr isn't responsible anymore for freeing the memory because the function I call took ownership. How do I get the shared_ptr to lose ownership?

The reason I want to have the shared_ptr lose ownership is that I want to use protocol buffer's AddAllocated functionality which takes an already allocated pointer and assumes ownership of it.

Example:

shared_ptr<MyProto> myProtoSharedPtr = // by this point this is the last reference to the heap allocated MyProto

// I want to add it to a collection and serialize the collection without copying
CollectionProto collectionProto;
collectionProto.mutable_my_proto().AddAllocated(myProtoSharedPtr.get()); // at this point collectionProto took ownership of the memory
std::string serialization = collectionProto.SerializeAsString();

// bad: myProtoSharedPtr.get() will be freed twice