Oligomer formation of histamine H2 receptors expressed in Sf9 and COS7 cells

A histamine H2 receptor, which had been mutated at its glycosylation site and tagged at its N-terminus with an HA tag (HA-H2 receptor), was expressed in Sf9 cells and COS7 cells. Immunoprecipitation and immunoblotting of HA-H2 receptors with αHA antibody revealed four bands of 31.5 ± 2.5 kDa, 59.0 ± 6.0 kDa, 80.5 ± 4.5 kDa and 120 kDa. These bands were also detected by immunoblot using anti-H2 receptor serum (C-terminus). In addition, H2 receptors without the HA-tag co-immunoprecipitated with HA-tagged H2 receptors devoid of the 51 C-terminal amino acids, via immunoprecipitation with αHA antibody, when the two receptors were coexpressed. These results suggest that H2 receptors are present as receptor oligomers and that the C-terminal portion is not involved in the formation of these oligomers.