Figure 1.

Specificity of angiotensin receptor antibodies and localization of angiotensin receptors in mitochondria of dopaminergic neurons. (a) The expression of major RAS components in dopaminergic neurons was confirmed by RT-PCR and laser microdissection of dopaminergic neurons retrogradly labeled by intrastriatal injection of fluorescent red retrobeads (RRB). SN section showing labeled dopaminergic neurons before and after laser microdissection for RT-PCR. Expression of TH, AGT, AT1, AT2 and β-actin mRNA in laser-microdissected dopaminergic neurons (right) and homogenates of SN used as a positive control (left) are also shown. (b) Western blot densitometric bands corresponding to 10 μg of AT1 or AT2 receptor overexpression lysate containing a C-terminal DDK epitope tag (DYKDDDDK) fused (left), and 10 μg of empty vector transfected control cell lysate HEK293 (EV, right). A band of 45 kDa was detected with the AT1 antibody, while a band of 50 kDa was detected with the AT2 antibody. A monoclonal antibody against DDK detected the corresponding band in the protein lysates. Colocalization of mitochondria and AT1 and AT2 receptors in primary cultures of the nigral region (c) and neurons from the MES 23.5 dopaminergic cell line (d). Electron microscopy of AT1 and AT2 labeling in a neuronal process (e) and cytoplasm (f) of a dopaminergic neuron. Immunolabeling for AT1 was observed in the outer membrane and cristae (white arrows) of mitochondria. In addition, strong AT1 labeling was also seen in clusters of free ribosomes (empty arrowheads). Immunolabeling for AT2 was present in mitochondrial membranes (white arrows), in the rough endoplasmic reticulum (black arrowheads) and in small clusters of free ribosomes, some of which were in close proximity to labeled mitochondria (empty arrowheads). AGT, angiotensinogen; DA, dopaminergic; MTDR, MitoTracker Deep Red; SN, substantia nigra; TH, tyrosine hydroxylase. Scale bars: (a) 50 and 200 μm (SN section); (c) 5 μm; (d) 10 μm; (e and f) 500 nm