No. As a consequence of containing components that need to be hosted over the USB interface the Gear VR locks the phone into USB host mode and thereby prevents it from becoming a slave to a PC, which is what is required for USB tethering.
However if you're trying to improve Riftcat streaming performance, and you have an S8, S8+ or a Note 8, and a Gear VR model with a multipurpose jack, you might consider experimenting with a USB to Ethernet adapter.