Pleckstrin homology-like domain family A-member 3 (PHLDA3) has recently been identified
as a player in adaptive and maladaptive cellular stress pathways. The outcome of PHLDA3
signalling was shown to vary across different cell types and states. It emerges that
its expression and protein level are highly increased in amyotrophic lateral sclerosis
(ALS) patient-derived astrocytes. Whether it orchestrates a supportive or detrimental
function remains unexplored in the context of neurodegenerative pathologies. To directly
address the role of PHLDA3 in healthy and ALS astrocytes, we used overexpression and
knockdown strategies. We generated cultures of primary mouse astrocytes and also human
astrocytes from control and ALS patient-derived induced pluripotent stem cells harbouring
the superoxide-dismutase 1 mutation. Then, we assessed astrocyte viability and the
impact of their secretome on oxidative stress responses in human stem cell-derived
cortical and spinal neuronal cultures. Here, we show that PHLDA3 overexpression or
knockdown in control astrocytes does not significantly affect astrocyte viability
or reactive oxygen species production. However, PHLDA3 knockdown in ALS astrocytes
diminishes reactive oxygen species concentrations in their supernatants, indicating
that PHLDA3 can facilitate stress responses in cells with altered homeostasis. In
support, supernatants of PHLDA3-silenced spinal ALS and even control spinal astrocytes
with a lower PHLDA3 protein content could prevent sodium arsenite-induced stress granule
formation in spinal neurons. Our findings provide evidence that reducing PHLDA3 levels
may transform astrocytes into a more neurosupportive state relevant to targeting non-cell
autonomous ALS pathology.
