Figure 3.

Inhibition of DLP1 function induces aberrant mitochondrial and ER phenotypes. Cells transfected with GFP-DLP1-K38A or GFP-DLP1-D231N or microinjected with inhibitory DLP1 antibodies were immunostained with antibodies to mitochondria (dihydrolipoamide acetyltransferase) and ER (PDI). (A) Cells expressing K38A show a reduction in uniform punctate DLP1 structures and the appearance of large aggregates. In the same cells, mitochondria appear to collapse toward the cell center, forming long tubules encircling the nucleus (A′, arrows) and losing the discrete size and shape observed in adjacent untransfected control cells. ER staining in these mutant cells is markedly reduced compared with that in adjacent untransfected control cells (A"). (B) Cells expressing D231N show a diffuse and markedly different distribution from cells expressing K38A or endogenous DLP1. Despite the difference in the distribution of the mutant D231N protein, these cells display the same aberrant mitochondrial (B′, arrows) and ER (B") phenotypes found in K38A-expressing cells. (C) A cell injected with DLP1 antibodies. The lower cell displays Cascade Blue–conjugated dextran concentrated in the nucleus and peripheral cytoplasm, confirming a successful injection. Mitochondrial staining in the same injected cell shows long tubular structures (C′, arrows) collapsed about the nucleus, similar to the aberrant mitochondria observed in the mutant cells. Note the collapse of the ER about the nucleus (C") and the reduced staining intensity, as in the mutant cells. N, nucleus of transfected or injected cells. Bar, 10 μm.