P73 and age-related diseases: is there any link with Parkinson Disease?

Abstract

P73 is a member of the p53 transcription factors family with a prominent role in neurobiology, affecting brain development as well as controlling neuronal survival. Accordingly, p73 has been identified as key player in many age-related neurodegenerative diseases, such as Alzheimer's disease, neuroAIDS and Niemann-Pick type C disease. Here we investigate possible correlations of p73 with Parkinson disease. Tyrosine hydroxylase is a crucial player in Parkinson disease being the enzyme necessary for dopamine synthesis. In this work we show that levels of tyrosine hydroxylase can be influenced by p73. We also demonstrate that p73 can protect against tyrosine hydroxylase depletion in an in vitro model of Parkinson disease.

Figure 1. Th promoter encodes for putative p73 responsive elements

Schematic representation of the p73 responsive elements in the promoter region of mouse tyrosine hydroxylase. Sequences with confidence of prediction ≥90% and indentified by all the predictive programs are reported, along with their sequence and position upstream than ATG start site.

Figure 2. Tyrosine hydroxylase levels correlates with p73

CGN primary cells were transiently transfected (as indicated) and 48 hours later, collected and processed. Real-time PCR result of Th levels (A) and of p73 levels (B) are depicted. Experiment has been reproduced at least 3 times (data are represented as mean +/− SD).

Figure 3. Tyrosine hydroxylase levels correlates with p73 transactivation potential

N2a cells were transiently transfected with human TAp73β or shRNAs specific for exon 13; 48 hours later, cells were collected and processed. Semi-quantitative PCR showed that knock-down of exon 13 lead to a shift from α to β (A). Real-time PCR shows an increase of about 5 times in Th levels (B). In order to test efficiency of transfection, p73 levels were monitored (C). Experiment has been reproduced at least 3 times (data are represented as mean +/− SD). KD = knock-down, GAPDH = Glyceraldehyde 3-phosphate dehydro-genase, untr. = untreated. Experiment has been reproduced at least 3 times.

Figure 4. p73 counteracts depletion of Th by 6-OHDA

N2a cells were transiently transfected with human TAp73 or shRNA against p73. After 48 hours, cells were treated with 10μM (final concentration) of 6-OHDA and collected at the indicated time points. Protein extracts were subjected to western blot analysis and quantified with densitometry. 6-OHDA = 6-hydroxydopamine, Th = tyrosine hydroxylase, GAPDH = Glyceraldehyde 3-phosphate dehydrogenase. Experiment has been reproduced at least 3 times.