Smart Grid (SG) is expected to use a variety of communications technologies as the underlying communications infrastructures. The interworking between heterogeneous communications network is crucial to support reliability and end-to-end features. In this paper, we consider a hybrid SG communications architecture that consists of a IEEE 802.11s mesh-based smart meter network and an LTE-based wide area network for collecting smart meter data. While a gateway can be used to bridge these networks, it will still not possible to pin point a smart meter directly from the utility control center nor running a TCP-based application that requires a connection establishment phase. We propose a gateway address translation based approach to enable execution of end-to-end protocols without making any changes to LTE and 802.11s mesh networks. Specifically, we introduce a new layer at the gateway which will perform the network address translation by using unique pseudonyms for the smart meters. In this way, we also ensure privacy of the consumer since the IP addresses of the smart meters are not exposed to utility company. We implemented the proposed mechanism under ns-3 network simulator which have libraries to support both IEEE 802.11s and LTE communications. The results indicate that we can achieve our goals without introducing any additional overhead.