The result shown here indicates that while both kinases can interact with Abp1, their mode of function, or their relevant substrates, may only be available at some endocytic sites. The question then arises as to what function Abp1 is performing at the endocytic sites. Over the years a number of functions have been ascribed to Abp1. Abp1 deletion in yeast cells causes a reduced invagination rate of endocytic sites, while overexpression of ABP1 is lethal. Biochemically an interaction with Aim3 has been shown to generate an actin capping function, while a function in Arp2/3 activation has also been described. Its SH3 domain has been shown to be important for localizing Ark1 and Prk1 to endocytic sites, though interestingly, lack of kinase localization per se does not causes a very severe phenotype on analysis of endocytic reporter behaviour. The data presented here suggests the possibility that Abp1 may function in a distinct, but overlapping endocytic pathway, that becomes the major internalization route, when the classic CME TH-302 pathway is inhibited. This pathways does not appear to require the dynamin like protein Vps1 or the Arf3 GAP Lsb5. Another possibility is that residual function of the classical CME pathway is responsible for the uptake of FM4-64 and Lucifer yellow that is observed. If there was a such a residual function, it might be expected that occasional invagination of Sla1-GFP would be detected, and that GFP-Snc1 would be observed in some cell compartments. This however is not the situation detected in these experiments. In addition, the level of uptake of FM4-64 appears largely unimpaired which is difficult to correlate with CME which is functioning at a basal level. Thus, we consider that the Abp1-dependent uptake route is unlikely to be simply poorly functioning CME. Given the absence of actin cables in the treated cells, it would also seem less likely that Abp1 is functioning within the formin– based alternative pathway as formins are generally considered to function in cable production. However, it remains a possibility that the increased actin dynamics precludes normal formin function in cable generation and allows these proteins to function in a distinct role in endocytosis. The alternative endocytic route identified here also shows a partial requirement for Sac6 and Rvs167. Sac6 is the yeast fimbrin homologue and is an actin bundling protein. Its ability to bind actin is necessary for invagination to occur. The bundling of filaments is considered to make a stronger structure to allow invagination to occur against.