Sharon wolf et al. wrote a beautiful paper characterizing these a few years ago. While their function is still relatively unclear, they identified membrane depolarization as a condition that disrupts their formation. https://elifesciences.org/articles/29929
We showed a physiological role for these calcium phosphate granules (described by Lehninger in the 1960s) in the response to acute hypoxia in this paper: https://www.nature.com/articles/s41586-020-2551-y
a) We saw that NCLX activation in acute hypoxia is driven by an increase in soluble matrix Ca2+.
Where does Ca2+ come from?
¡Surprise!😃
Ca2+ is already inside the mitochondrial matrix, in calcium phosphate granules that are dissolved in hypoxia (due to acidification) releasing soluble Ca2+
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I've also seen them in HUVEC data on the cryoET data portal.
e.g.
https://cryoetdataportal.czscience.com/runs/9234
https://cryoetdataportal.czscience.com/runs/9124
https://www.nature.com/articles/s41586-020-2551-y
A post in twitter showing the granules:
https://x.com/tonnomartinez/status/1288502818777833474
(also copied in a response to this post 👇)
Where does Ca2+ come from?
¡Surprise!😃
Ca2+ is already inside the mitochondrial matrix, in calcium phosphate granules that are dissolved in hypoxia (due to acidification) releasing soluble Ca2+