The subcellular compartmentalization of kinase activity allows for regulation of distinct cellular processes involved in cell differentiation or survival. The PTEN-induced kinase-1 (PINK1) is a neuroprotective kinase localized to cytosolic and mitochondrial compartments. While mitochondrial targeting of PINK1 is important for its activities regulating mitochondrial homeostasis, the physiological role of the cytosolic pool of PINK1 remains unknown. Here, we demonstrate a novel role for cytosolic PINK1 in neuronal differentiation/neurite maintenance. Overexpression of wild-type PINK1, but not a catalytically inactive form of PINK1(K219M), promoted neurite outgrowth in SH-SY5Y cells and increased dendritic lengths in primary cortical and midbrain dopaminergic neurons. To identify the subcellular pools of PINK1 involved in promoting neurite outgrowth, we transiently transfected cells with PINK1 constructs designed to target PINK1 to the outer mitochondrial membrane (OMM-PINK1), or restrict PINK1 to the cytosol (ΔN111-PINK1). Both constructs blocked cell death associated with loss of endogenous PINK1. However, transient expression of ΔN111-PINK1, but not of OMM-PINK1 or ΔN111-PINK1(K219M), promoted dendrite outgrowth in primary neurons, and rescued the decreased dendritic arborization of PINK1-deficient neurons. Mechanistically, the cytosolic pool of PINK1 regulated neurite morphology through enhanced anterograde transport of dendritic mitochondria and amplification of PKA-related signaling pathways. Our data supports a novel role for PINK1 in regulating dendritic morphogenesis.

Mutations in PTEN-induced kinase 1 (PINK1) are associated with a familial syndrome related to Parkinson’s disease (PD). We previously reported that stable neuroblastoma SH-SY5Y cell lines with reduced expression of endogenous PINK1 exhibit mitochondrial fragmentation, increased mitochondria-derived superoxide, induction of compensatory macroautophagy/mitophagy and a low level of ongoing cell death. Here, we investigated the ability of protein kinase A (PKA) to confer protection in this model, focusing on its subcellular targeting. Either: 1) treatment with pharmacological PKA activators; 2) transient expression of a constitutively active form of mitochondria-targeted PKA; or 3) transient expression of wild-type AKAP1, a scaffold that targets endogenous PKA to mitochondria, reversed each of the phenotypes attributed to loss of PINK1 in SH-SY5Y cells, and rescued parameters of mitochondrial respiratory dysfunction. Mitochondrial and lysosomal changes in primary cortical neurons derived from PINK1 knockout mice or subjected to PINK1 RNAi were also reversed by activation of PKA. PKA phosphorylates the rat dynamin-related protein 1 isoform 1 (Drp1) at serine 656 (homologous to human serine 637), inhibiting its pro-fission function. Mimicking phosphorylation of Drp1 recapitulated many of the protective effects of AKAP1/PKA. These data indicate that redirecting endogenous PKA to mitochondria can compensate for deficiencies in PINK1 function, highlighting the importance of compartmentalized signaling networks in mitochondrial quality control.