Link to bioRxiv paper:

http://biorxiv.org/cgi/content/short/2020.09.17.301903v1?rss=1

Authors: Sun, Y., Gupta, M. K., Stenson, K., Mohan, M. L., Wanner, N., Asosinght, K., Erzurum, S., Naga Prasad, S. N.

Abstract:

Ischemia/hypoxia is major underlying cause for heart failure and stroke. Although beta-adrenergic receptor ({beta}AR) is phosphorylated in response to hypoxia, less is known about the underlying mechanisms. Hypoxia results in robust GRK2-mediated {beta}2AR phosphorylation but does not cause receptor internalization. However, hypoxia leads to significant endosomal-{beta}2AR phosphorylation accompanied by inhibition of {beta}2AR-associated protein phosphatase 2A (PP2A) activity impairing resensitization. Phosphoinositide 3-kinase {gamma} (PI3K{gamma}) impedes resensitization by phosphorylating endogenous inhibitor of protein phosphatase 2A, I2PP2A that inhibits PP2A activity. Hypoxia increased PI3K{gamma} activity leading to significant phosphorylation of I2PP2A resulting in inhibition of PP2A and consequently resensitization. Surprisingly, {beta}-blocker abrogated hypoxia-mediated {beta}2AR phosphorylation instead of phosphorylation in normoxia. Subjecting mice to hypoxia leads to significant cardiac dysfunction and {beta}2AR phosphorylation showing conservation of non-canonical hypoxia-mediated pathway in vivo. These findings provide mechanistic insights on hypoxia-mediated {beta}AR dysfunction which is rescued by {beta}-blocker and will have significant implications in heart failure and stroke.

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