Protein kinase A determines platelet life span and survival by regulating apoptosis
Lili Zhao, … , Changgeng Ruan, Kesheng Dai
Lili Zhao, … , Changgeng Ruan, Kesheng Dai
Published October 30, 2017
Citation Information: J Clin Invest. 2017;127(12):4338-4351. https://doi.org/10.1172/JCI95109.
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Research Article Hematology

Protein kinase A determines platelet life span and survival by regulating apoptosis

Abstract

Apoptosis delimits platelet life span in the circulation and leads to storage lesion, which severely limits the shelf life of stored platelets. Moreover, accumulating evidence indicates that platelet apoptosis provoked by various pathological stimuli results in thrombocytopenia in many common diseases. However, little is known about how platelet apoptosis is initiated or regulated. Here, we show that PKA activity is markedly reduced in platelets aged in vitro, stored platelets, and platelets from patients with immune thrombocytopenia (ITP), diabetes, and bacterial infections. Inhibition or genetic ablation of PKA provoked intrinsic programmed platelet apoptosis in vitro and rapid platelet clearance in vivo. PKA inhibition resulted in dephosphorylation of the proapoptotic protein BAD at Ser155, resulting in sequestration of prosurvival protein BCL-XL in mitochondria and subsequent apoptosis. Notably, PKA activation protected platelets from apoptosis induced by storage or pathological stimuli and elevated peripheral platelet levels in normal mice and in a murine model of ITP. Therefore, these findings identify PKA as a homeostatic regulator of platelet apoptosis that determines platelet life span and survival. Furthermore, these results suggest that regulation of PKA activity represents a promising strategy for extending platelet shelf life and has profound implications for the treatment of platelet number-related diseases and disorders.

Authors

Lili Zhao, Jun Liu, Chunyan He, Rong Yan, Kangxi Zhou, Qingya Cui, Xingjun Meng, Xiaodong Li, Yang Zhang, Yumei Nie, Yang Zhang, Renping Hu, Yancai Liu, Lian Zhao, Mengxing Chen, Weiling Xiao, Jingluan Tian, Yunxiao Zhao, Lijuan Cao, Ling Zhou, Anning Lin, Changgeng Ruan, Kesheng Dai

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Figure 1

PKA activity is reduced in stored platelets or platelets from patients with ITP, diabetes, and sepsis.

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PKA activity is reduced in stored platelets or platelets from patients w...
(A and B) Western blot analysis of phosphorylated GPIbβ at Ser166 (pGPIbβ) in freshly isolated (0 hours, control) or in vitro–aged (16 hours) platelets (left). Densitometry of immunoblots for pGPIbβ from Western blot data (right) (A). PKA activity in the platelets was examined by ELISA (B). Data are expressed as mean ± SD from 4 independent experiments. *P < 0.05; **P < 0.01, Student’s t test. (C and D) Washed platelets were incubated at 22°C for indicated times. Representative immunoblots and quantification for pGPIbβ (C) and PKA activity (D) are shown. Data are represented as mean ± SD from 4 independent experiments. **P < 0.01; #P < 0.001 compared with controls (0 hours by 1-way ANOVA. (E–J) Platelets were isolated from patients with ITP (E and F), diabetes (G and H), and sepsis (I and J) and age- and sex-matched healthy controls. Representative immunoblots and quantification for pGPIbβ (E, G, and I) and PKA activity (F, H, and J) are shown. Data in each figure are expressed as mean ± SD from 6 patients and controls. *P < 0.05; **P < 0.01; #P < 0.001, compared with controls, Student’s t test. (K and L) Washed platelets were incubated with indicated bacteria (1:20) or vehicle control at 37°C for 90 minutes. Representative immunoblots and quantification for pGPIbβ (K) and PKA activity (L) are shown. Data are expressed as mean ± SD from 4 independent experiments. *P < 0.05; **P < 0.01, compared with control, Student’s t test.