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Pik3ip1 modulates cardiac hypertrophy by inhibiting PI3K pathway.

Song HK, Kim J, Lee JS, Nho KJ, Jeong HC, Kim J, Ahn Y, Park WJ, Kim do H - PLoS ONE (2015)

Bottom Line: We found that the expression level of Pik3ip1 was markedly higher in cardiomyocytes than in fibroblasts.Pik3ip1 deficiency was shown to lead to activation of PI3K/protein kinase B (AKT)/ mammalian target of rapamycin (mTOR) signaling pathway, increasing protein synthesis and cell size.Collectively, our results elucidate the mechanisms for the roles of Pik3ip1 in PI3K/AKT signaling pathway.

View Article: PubMed Central - PubMed

Affiliation: School of Life Sciences and Systems Biology Research Center, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea.

ABSTRACT
Cardiac hypertrophy is an adaptive response to various physiological and pathological stimuli. Phosphoinositide-3 kinase (PI3K) is a highly conserved lipid kinase involved in physiological cardiac hypertrophy (PHH). PI3K interacting protein1 (Pik3ip1) shares homology with the p85 regulatory subunit of PI3K and is known to interact with the p110 catalytic subunit of PI3K, leading to attenuation of PI3K activity in liver and immune cells. However, the role of Pik3ip1 in the heart remains unknown. In the present study, the effects of Pik3ip1 on cardiac hypertrophy were examined. We found that the expression level of Pik3ip1 was markedly higher in cardiomyocytes than in fibroblasts. The interaction of Pik3ip1 with the p110a subunit of PI3K in the heart was identified by immunoprecipitation using neonatal rat cardiomyocytes (NRCM). Approximately 35% knockdown of Pik3ip1 was sufficient to induce myocardial hypertrophy. Pik3ip1 deficiency was shown to lead to activation of PI3K/protein kinase B (AKT)/ mammalian target of rapamycin (mTOR) signaling pathway, increasing protein synthesis and cell size. However, adenovirus-mediated overexpression of Pik3ip1 attenuated PI3K-mediated cardiac hypertrophy. Pik3ip1 was upregulated by PHH due to swimming training, but not by pathological cardiac hypertrophy (PAH) due to pressure-overload, suggesting that Pik3ip1 plays a compensatory negative role for PHH. Collectively, our results elucidate the mechanisms for the roles of Pik3ip1 in PI3K/AKT signaling pathway.

No MeSH data available.


Related in: MedlinePlus

Pik3ip1 expression was upregulated in 4-weeks exercise-induced hypertrophic hearts.(A) qRT-PCR analysis of transcripts for Pik3ip1 in 1-week TAC, 2-weeks TAC, 2-weeks exercised and 4-weeks exercised mice hearts. mRNA expression was normalized to 18S. (n = 3, ** p < 0.01 compared with compared with the Sham or Sedentary mice, t test). (B) Representative immunoblot images p110α, AKT, Pik3ip1 and α-tubulin protein expression in 1-week TAC, 2-weeks TAC, 2-weeks exercised and 4-weeks exercised mice hearts. (C) Quantification of Pik3ip1 and p110α protein expression in 1-week TAC, 2-weeks TAC, 2-weeks exercised and 4-weeks exercised mice hearts.α-tubulin served as an internal control. (n = 3, * p < 0.05 compared with the Sham or Sedentary mice, t test) (D) Quantification of phosphorylated AKT in 1-week TAC, 2-weeks TAC, 2-weeks exercised and 4-weeks exercised mice hearts. Total AKT served as a control. (n = 3, * p < 0.05 compared with the Sham or Sedentary mice, t test).
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pone.0122251.g006: Pik3ip1 expression was upregulated in 4-weeks exercise-induced hypertrophic hearts.(A) qRT-PCR analysis of transcripts for Pik3ip1 in 1-week TAC, 2-weeks TAC, 2-weeks exercised and 4-weeks exercised mice hearts. mRNA expression was normalized to 18S. (n = 3, ** p < 0.01 compared with compared with the Sham or Sedentary mice, t test). (B) Representative immunoblot images p110α, AKT, Pik3ip1 and α-tubulin protein expression in 1-week TAC, 2-weeks TAC, 2-weeks exercised and 4-weeks exercised mice hearts. (C) Quantification of Pik3ip1 and p110α protein expression in 1-week TAC, 2-weeks TAC, 2-weeks exercised and 4-weeks exercised mice hearts.α-tubulin served as an internal control. (n = 3, * p < 0.05 compared with the Sham or Sedentary mice, t test) (D) Quantification of phosphorylated AKT in 1-week TAC, 2-weeks TAC, 2-weeks exercised and 4-weeks exercised mice hearts. Total AKT served as a control. (n = 3, * p < 0.05 compared with the Sham or Sedentary mice, t test).

Mentions: We examine Pik3ip1expression level in these animal models. The results showed that Pik3ip1 was significantly upregulated in the 4-weeks exercised model both at the mRNA and protein levels (Fig 6A–6C). However, no significant change in Pik3ip1 expression was observed in the 2-weeks exercise, 1-week, and 2-weeks TAC animals (Fig 6A–6C). Because Pik3ip1 is a negative regulator of PI3K, we measured p110α expression and AKT phosphorylation. As shown in Fig 6B and 6C, p110α expression increased in both exercise models. Two-weeks TAC and exercised mice presented an increase in AKT phosphorylation. However, AKT phosphorylation was attenuated in the heart of 4-weeks exercised mice although p110α was increased. We next examined Pik3ip1expression level in myocytes and fibroblasts in the heart of 2-weeks TAC and 4-weeks exercised mice. In 2-weeks TAC operated mouse hearts, Pik3ip1 expression was not changed in both the cell types. However, Pik3ip1 expression was upregulated in myocytes, but not in the fibroblasts in the heart of 4-weeks exercised mice (Fig F in S1 File). These data suggest that the increased Pik3ip1 in myocytes from 4-weeks exercised mice could contribute to the attenuation of AKT phosphorylation.


Pik3ip1 modulates cardiac hypertrophy by inhibiting PI3K pathway.

Song HK, Kim J, Lee JS, Nho KJ, Jeong HC, Kim J, Ahn Y, Park WJ, Kim do H - PLoS ONE (2015)

Pik3ip1 expression was upregulated in 4-weeks exercise-induced hypertrophic hearts.(A) qRT-PCR analysis of transcripts for Pik3ip1 in 1-week TAC, 2-weeks TAC, 2-weeks exercised and 4-weeks exercised mice hearts. mRNA expression was normalized to 18S. (n = 3, ** p < 0.01 compared with compared with the Sham or Sedentary mice, t test). (B) Representative immunoblot images p110α, AKT, Pik3ip1 and α-tubulin protein expression in 1-week TAC, 2-weeks TAC, 2-weeks exercised and 4-weeks exercised mice hearts. (C) Quantification of Pik3ip1 and p110α protein expression in 1-week TAC, 2-weeks TAC, 2-weeks exercised and 4-weeks exercised mice hearts.α-tubulin served as an internal control. (n = 3, * p < 0.05 compared with the Sham or Sedentary mice, t test) (D) Quantification of phosphorylated AKT in 1-week TAC, 2-weeks TAC, 2-weeks exercised and 4-weeks exercised mice hearts. Total AKT served as a control. (n = 3, * p < 0.05 compared with the Sham or Sedentary mice, t test).
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pone.0122251.g006: Pik3ip1 expression was upregulated in 4-weeks exercise-induced hypertrophic hearts.(A) qRT-PCR analysis of transcripts for Pik3ip1 in 1-week TAC, 2-weeks TAC, 2-weeks exercised and 4-weeks exercised mice hearts. mRNA expression was normalized to 18S. (n = 3, ** p < 0.01 compared with compared with the Sham or Sedentary mice, t test). (B) Representative immunoblot images p110α, AKT, Pik3ip1 and α-tubulin protein expression in 1-week TAC, 2-weeks TAC, 2-weeks exercised and 4-weeks exercised mice hearts. (C) Quantification of Pik3ip1 and p110α protein expression in 1-week TAC, 2-weeks TAC, 2-weeks exercised and 4-weeks exercised mice hearts.α-tubulin served as an internal control. (n = 3, * p < 0.05 compared with the Sham or Sedentary mice, t test) (D) Quantification of phosphorylated AKT in 1-week TAC, 2-weeks TAC, 2-weeks exercised and 4-weeks exercised mice hearts. Total AKT served as a control. (n = 3, * p < 0.05 compared with the Sham or Sedentary mice, t test).
Mentions: We examine Pik3ip1expression level in these animal models. The results showed that Pik3ip1 was significantly upregulated in the 4-weeks exercised model both at the mRNA and protein levels (Fig 6A–6C). However, no significant change in Pik3ip1 expression was observed in the 2-weeks exercise, 1-week, and 2-weeks TAC animals (Fig 6A–6C). Because Pik3ip1 is a negative regulator of PI3K, we measured p110α expression and AKT phosphorylation. As shown in Fig 6B and 6C, p110α expression increased in both exercise models. Two-weeks TAC and exercised mice presented an increase in AKT phosphorylation. However, AKT phosphorylation was attenuated in the heart of 4-weeks exercised mice although p110α was increased. We next examined Pik3ip1expression level in myocytes and fibroblasts in the heart of 2-weeks TAC and 4-weeks exercised mice. In 2-weeks TAC operated mouse hearts, Pik3ip1 expression was not changed in both the cell types. However, Pik3ip1 expression was upregulated in myocytes, but not in the fibroblasts in the heart of 4-weeks exercised mice (Fig F in S1 File). These data suggest that the increased Pik3ip1 in myocytes from 4-weeks exercised mice could contribute to the attenuation of AKT phosphorylation.

Bottom Line: We found that the expression level of Pik3ip1 was markedly higher in cardiomyocytes than in fibroblasts.Pik3ip1 deficiency was shown to lead to activation of PI3K/protein kinase B (AKT)/ mammalian target of rapamycin (mTOR) signaling pathway, increasing protein synthesis and cell size.Collectively, our results elucidate the mechanisms for the roles of Pik3ip1 in PI3K/AKT signaling pathway.

View Article: PubMed Central - PubMed

Affiliation: School of Life Sciences and Systems Biology Research Center, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea.

ABSTRACT
Cardiac hypertrophy is an adaptive response to various physiological and pathological stimuli. Phosphoinositide-3 kinase (PI3K) is a highly conserved lipid kinase involved in physiological cardiac hypertrophy (PHH). PI3K interacting protein1 (Pik3ip1) shares homology with the p85 regulatory subunit of PI3K and is known to interact with the p110 catalytic subunit of PI3K, leading to attenuation of PI3K activity in liver and immune cells. However, the role of Pik3ip1 in the heart remains unknown. In the present study, the effects of Pik3ip1 on cardiac hypertrophy were examined. We found that the expression level of Pik3ip1 was markedly higher in cardiomyocytes than in fibroblasts. The interaction of Pik3ip1 with the p110a subunit of PI3K in the heart was identified by immunoprecipitation using neonatal rat cardiomyocytes (NRCM). Approximately 35% knockdown of Pik3ip1 was sufficient to induce myocardial hypertrophy. Pik3ip1 deficiency was shown to lead to activation of PI3K/protein kinase B (AKT)/ mammalian target of rapamycin (mTOR) signaling pathway, increasing protein synthesis and cell size. However, adenovirus-mediated overexpression of Pik3ip1 attenuated PI3K-mediated cardiac hypertrophy. Pik3ip1 was upregulated by PHH due to swimming training, but not by pathological cardiac hypertrophy (PAH) due to pressure-overload, suggesting that Pik3ip1 plays a compensatory negative role for PHH. Collectively, our results elucidate the mechanisms for the roles of Pik3ip1 in PI3K/AKT signaling pathway.

No MeSH data available.


Related in: MedlinePlus