Akt1/protein kinase Bα is critical for ischemic and VEGF-mediated angiogenesis
Eric Ackah, … , Kenneth Walsh, William C. Sessa
Eric Ackah, … , Kenneth Walsh, William C. Sessa
Published August 1, 2005
Citation Information: J Clin Invest. 2005;115(8):2119-2127. https://doi.org/10.1172/JCI24726.
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Categories: Research Article Vascular biology

Akt1/protein kinase Bα is critical for ischemic and VEGF-mediated angiogenesis

Abstract

Akt, or protein kinase B, is a multifunctional serine-threonine protein kinase implicated in a diverse range of cellular functions including cell metabolism, survival, migration, and gene expression. However, the in vivo roles and effectors of individual Akt isoforms in signaling are not explicitly clear. Here we show that the genetic loss of Akt1, but not Akt2, in mice results in defective ischemia and VEGF-induced angiogenesis as well as severe peripheral vascular disease. Akt1 knockout (Akt1–/–) mice also have reduced endothelial progenitor cell (EPC) mobilization in response to ischemia, and reintroduction of WT EPCs, but not EPCs isolated from Akt1–/– mice, into WT mice improves limb blood flow after ischemia. Mechanistically, the loss of Akt1 reduces the basal phosphorylation of several Akt substrates, the migration of fibroblasts and ECs, and NO release. Reconstitution of Akt1–/– ECs with Akt1 rescues the defects in substrate phosphorylation, cell migration, and NO release. Thus, the Akt1 isoform exerts an essential role in blood flow control, cellular migration, and NO synthesis during postnatal angiogenesis.

Authors

Eric Ackah, Jun Yu, Stefan Zoellner, Yasuko Iwakiri, Carsten Skurk, Rei Shibata, Noriyuki Ouchi, Rachael M. Easton, Gennaro Galasso, Morris J. Birnbaum, Kenneth Walsh, William C. Sessa

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Figure 1

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Characterization of tissue and vascular expression of Akt1 and Akt2. (A)...
Characterization of tissue and vascular expression of Akt1 and Akt2. (A) RT-PCR analysis of RNA isolated from mouse lung fibroblasts using Akt1-, Akt2-, and Hsp90-specific primers. (B) Expression of Akt1 and Akt2 protein in homogenates from heart and gastrocnemius muscle by Western blot with antibodies against Akt1, Akt2, or Hsp90 as a loading control. (C) Akt1 and Akt2 expression in various blood vessels by Western blot using antibodies against Akt1, Akt2, and β-actin as a loading control. (D) p-Akt levels in various blood vessels from WT, Akt1–/–, and Akt2–/– mice. Lysates from 3 animals per group were pooled and analyzed by Western blot using p-AktS473– and p-AktT308–specific Akt antibodies. (E) Relative expression of Akt isoforms in blood vessels. Lysates from WT mice were analyzed by SDS-PAGE and quantitative Western blot. Relative protein amounts of Akt1 and Akt2 in the vessels were quantified using standard curves obtained by running recombinant mouse Akt1 and Akt2 proteins. Data represent the mean of 2 pooled samples; n = 3.