The involvement of dynamin in macropinocytosis is not clear and studies investigating its role have given conflicting results [55, 58, 69, 70, 77, 78] . Similarly, viruses that use macropinocytosis for infection display different sensitivities to dynamin inhibition [69, 70] . Our studies showed that a DN mutant of the 'aa' splice variant of dynamin-2 does not inhibit BTV-1 uptake or infection of BHK cells. This DN mutant was shown to inhibit uptake of transferrin (see Fig. 4 ) but not dextran (data not shown), indicating that macropinocytosis/fluid-phase uptake, but not CME is active in BHK cells expressing this mutant. These observations are consistent with recent studies by Cao et al., (2007) which show that different splice variants of dynamin-2 regulate different endocytosis pathways, and that expression of a DN mutant of the 'aa' splice variant of dynamin-2 resulted in attenuation of transferrin, but not dextran uptake [55] . In contrast, BTV-1 uptake was inhibited by the dynamin inhibitor, dynasore. Since it is likely that dynasore inhibits all forms of dynamin, this observation suggests that the mechanism used by BTV-1 to enter BHK cells is dynamin dependent but relies on a form of dynamin that cannot be inhibited by DN mutants of the 'aa' splice variant of dynamin-2.