Figure 3.

SARM associates with neuronal mitochondria. A, A SARM-Venus fusion protein (SARM-V) expressed in cortical neurons colocalizes with mitochondria-targeted DSRed protein (mitoDSRed) in both soma and neurites. B, DRG axons expressing mitoDSRed and SARM-V show mitochondrial colocalization. C, Immunostaining of endogenous SARM in DRG axons shows colocalization with mitoDSRed. A lack of immunoreactivity in SARM^−/− axons (bottom left) verifies the specificity of the antibody used. D, SARMΔN27 mutant is localized diffusely in DRG axons and does not colocalize with mitoDSRed protein. E, SARM-V cofractionates with mitochondrial resident proteins Opa1 and Tom40. Treatment of mitochondrial and cytosolic fractions with proteinase K leads to proteolysis of SARM but not Opa1 or Tom40, indicating SARM-V resides outside the mitochondria. F, SARM lacking residues 2–27 (SARMΔN27-V) predominantly fractionates with cytosolic protein (ex.Hsp90). Scale bars, 10 μm.