2451 Mitophagy in the Myocardium tochondrial receptor for Parkin. 24 PINK1 can also phosphorylate MIRO, an atypical Rho GTPase that tethers mitochondria to the tubulin network. Phosphorylation of MIRO1 by PINK1 leads to ubiquitination by Parkin and proteosomal degradation, isolating damaged mitochondria from tubulin transport and the mitochondrial network. 25 Surprisingly, the PINK1/Parkin axis also regulates turnover of specific respiratory chain components, suggesting additional roles for the PINK1/Parkin pathway in regulating mitophagy. 26 A new study by Fu et al27 has revealed that other E3 ubiquitin ligases are involved in the regulation of mitophagy. This study demonstrated that glycoprotein 78 (GP78) mediates destruction of mitofusins in the setting of mitochondrial damage/depolarization, leading to mitochondrial fragmentation and autophagy. This E3 ligase pathway operates in Parkin-null cells, showing overlapping patterns of mitophagy regulation by independently functioning ubiquitin ligases. 27