ATM controls improved DNA repair and mitochondria transfer between neighboring cells

Introduction:

In multicellular tissue, the cells communicate constantly with their environment including neighboring cells as well the extracellular matrix by giving and receiving signals for their vitality and homeostasis. Accumulated evidence has shown the exposure to genotoxic agents such as ionizing radiation can be detrimental in non–target bystander cell, however, little is known mechanistically about the prosurvival impact of unexposed neighboring cells on genotoxically injured cells. In this study, we explored how feedback signals from non–target cells facilitate the dynamic of mitochondrial fusion and fission and modify DNA damage repair in genotoxically damaged target cells.

Methods:

We performed super resolution 3D imaging in combination with cell biological, biochemical and biophysical methods in a coculture model system deployed of different cell types (MiaPaCa 2 human pancreatic cancer cells; ATM wildtype (wt) and ATM knockout fibroblasts, as well ATM and DNA-PK inhibitor treated ATM wt). We tracked fluorescently labeled mitochondria in living cells and analyzed their morphology upon irradiation with or without combination of pharmaceutical compounds treatment. We further measured the foci resolution dynamics in cells exposed to x-rays (i.e. target cells), which were cultured in the presence or absence of undamaged cells using different markers (53BP1, phospho–Histone H2A.X S193 (γ–H2AX), phospho–ATM S1981 and phospho–DNA PKcs S2056).

Results:

Our data show that (i) bilateral transfer of mitochondria between target (irradiated) and non-target cells occurs in a ATM-dependently manner; (ii) DNA damage repair in target (irradiated) cells is accelerated through the presence of non-target cells in both not only in ATM wt and cells but also in ATM deficient fibroblastscells; (iii) cell cycle distribution in target cells is substantially different in co–cultured target cells as compared to mono-cultures of target cells; and (iv)a functional microtubules system is required for this intercellular signaling through direct cell–to–cell contact.

Conclusion:

Our data suggest that ATM is be a key determinant transducer for DNA damage repair in in cell–to–cell communication. ATM provides yet to be identified cues that signaling regulates radiogenic DNA damage repair in neighboring target cells, and intercellular mitochondria transfer in a manner dependent on the microtubules system. and It benefits the fusion between radiation damaged and healthy mitochondria restoring a healthy mitochondria system, which originated from different cell populations. from non-target to target cells in a manner dependent on the microtubule system. Consequently, normal cells support each other in surviving radiogenic DNA damage, while cancer cells might be prone to develop resistances to current radiochemotherapies – all of which are critical for general survival of multicellular organs including tumors.