OBJECTIVE: Diabetes results from a deficiency of functional beta-cells. Previous studies have identified hepatocyte growth factor (HGF) and parathyroid hormone-related protein (PTHrP) as two potent beta-cell mitogens. The objective of this study is to determine 1) whether HGF and PTHrP have additive/synergistic effects on beta-cell growth and proliferation; 2) the signaling pathways through which these growth factors mediate beta-cell mitogenesis; and 3) whether activation of this/these signaling pathway(s) enhances human beta-cell replication. RESEARCH DESIGN AND METHODS: We generated and phenotypically analyzed doubly transgenic mice overexpressing PTHrP and HGF in the beta-cell. INS-1 and primary mouse and human islet cells were used to identify mitogenic signaling pathways activated by HGF and/or PTHrP. RESULTS: Combined overexpression of HGF and PTHrP in the beta-cell of doubly transgenic mice did not result in additive/synergistic effects on beta-cell growth and proliferation, suggesting potential cross-talk between signaling pathways activated by both growth factors. Examination of these signaling pathways in INS-1 cells revealed atypical protein kinase C (PKC) as a novel intracellular target activated by both HGF and PTHrP in beta-cells. Knockdown of PKC zeta, but not PKC iota/lambda, expression using specific small-interfering RNAs blocked growth factor-induced INS-1 cell proliferation. Furthermore, adenovirus-mediated delivery of kinase-dead PKC zeta completely inhibited beta-cell proliferation in primary islet cells overexpressing PTHrP and/or HGF. Finally, adenovirus-mediated delivery of constitutively active PKC zeta in mouse and human primary islet cells significantly enhanced beta-cell proliferation. CONCLUSIONS: PKC zeta is essential for PTHrP- and HGF-induced beta-cell proliferation. PKC zeta activation could be useful in therapeutic strategies for expanding beta-cell mass in vitro and in vivo.
OBJECTIVE:Diabetes results from a deficiency of functional beta-cells. Previous studies have identified hepatocyte growth factor (HGF) and parathyroid hormone-related protein (PTHrP) as two potent beta-cell mitogens. The objective of this study is to determine 1) whether HGF and PTHrP have additive/synergistic effects on beta-cell growth and proliferation; 2) the signaling pathways through which these growth factors mediate beta-cell mitogenesis; and 3) whether activation of this/these signaling pathway(s) enhances human beta-cell replication. RESEARCH DESIGN AND METHODS: We generated and phenotypically analyzed doubly transgenic mice overexpressing PTHrP and HGF in the beta-cell. INS-1 and primary mouse and human islet cells were used to identify mitogenic signaling pathways activated by HGF and/or PTHrP. RESULTS: Combined overexpression of HGF and PTHrP in the beta-cell of doubly transgenic mice did not result in additive/synergistic effects on beta-cell growth and proliferation, suggesting potential cross-talk between signaling pathways activated by both growth factors. Examination of these signaling pathways in INS-1 cells revealed atypical protein kinase C (PKC) as a novel intracellular target activated by both HGF and PTHrP in beta-cells. Knockdown of PKC zeta, but not PKC iota/lambda, expression using specific small-interfering RNAs blocked growth factor-induced INS-1 cell proliferation. Furthermore, adenovirus-mediated delivery of kinase-dead PKC zeta completely inhibited beta-cell proliferation in primary islet cells overexpressing PTHrP and/or HGF. Finally, adenovirus-mediated delivery of constitutively active PKC zeta in mouse and human primary islet cells significantly enhanced beta-cell proliferation. CONCLUSIONS:PKC zeta is essential for PTHrP- and HGF-induced beta-cell proliferation. PKC zeta activation could be useful in therapeutic strategies for expanding beta-cell mass in vitro and in vivo.
Authors: Juan C Alvarez-Perez; Taylor C Rosa; Gabriella P Casinelli; Shelley R Valle; Jayalakshmi Lakshmipathi; Carolina Rosselot; Francisco Rausell-Palamos; Rupangi C Vasavada; Adolfo García-Ocaña Journal: Mol Endocrinol Date: 2014-12
Authors: José A González-Pertusa; John Dubé; Shelley R Valle; Taylor C Rosa; Karen K Takane; José M Mellado-Gil; Germán Perdomo; Rupangi C Vasavada; Adolfo García-Ocaña Journal: Endocrinology Date: 2010-02-22 Impact factor: 4.736
Authors: Nagesha Guthalu Kondegowda; Sheela Joshi-Gokhale; George Harb; Katoura Williams; Xiao Ying Zhang; Karen K Takane; Pili Zhang; Donald K Scott; Andrew F Stewart; Adolfo Garcia-Ocaña; Rupangi C Vasavada Journal: Diabetes Date: 2010-09-28 Impact factor: 9.461
Authors: Nathalie Fiaschi-Taesch; Todd A Bigatel; Brian Sicari; Karen K Takane; Fatima Salim; Silvia Velazquez-Garcia; George Harb; Karen Selk; Irene Cozar-Castellano; Andrew F Stewart Journal: Diabetes Date: 2009-01-09 Impact factor: 9.461