Domain requirements for an endocytosis-independent, isoform-specific function of dynamin-2.
Endocytosis is inhibited by overexpression of either dynamin-1 or dynamin-2 mutants because both isoforms form heterotetramers with endogenous dynamin-2 and interfere with its function. By contrast, other phenotypes, which are specifically triggered by overexpression of dynamin-2, but not dynamin-1 are likely to reflect endocytosis-independent, dynamin-2-specific functions and/or interactions. Using Dyn2/Dyn1 chimeras, we explored the structural requirements for a readily quantifiable, isoform-specific function of dynamin-2, the activation of caspase-3 to trigger apoptosis. Strikingly, swapping the highly homologous GTPase domain of dynamin-2 into dynamin-1 was sufficient to confer caspase-3 activation. Moreover, assembly-defective mutations in GED, dynamin's GAP/assembly domain, that inhibit endocytosis enhance caspase-3 activation. Thus, this dynamin-2-specific function is mechanistically distinct from and independent of its role in endocytosis. These findings have important implications for interpreting dynamin-2 dependent phenotypes in overexpression studies.
Soulet
Fabienne
F
Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
Schmid
Sandra L
SL
Damke
Hanna
H
D000818:Animals; D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism; D034284:Dynamin I / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D034285:Dynamin II / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004705:Endocytosis / Q000502:physiology*; D004789:Enzyme Activation; D006367:HeLa Cells; D006801:Humans; D011487:Protein Conformation; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D014168:Transferrin / Q000378:metabolism
D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D014168:Transferrin; D053148:Caspase 3; D034284:Dynamin I; D034285:Dynamin II