Angiotensin II modulates calponin gene expression in rat vascular smooth muscle cells in vivo

Calponin isoforms CNN1, CNN2 and CNN3: Regulators for actin cytoskeleton functions in smooth muscle and non-muscle cells

Calponin is an actin filament-associated regulatory protein expressed in smooth muscle and many types of non-muscle cells. Three homologous genes, CNN1, CNN2 and CNN3, encoding calponin isoforms 1, 2, and 3, respectively, are present in vertebrate species. All three calponin isoforms are actin-binding proteins with functions in inhibiting actin-activated myosin ATPase and stabilizing the actin cytoskeleton, while each isoform executes different physiological roles based on their cell type-specific expressions. Calponin 1 is specifically expressed in smooth muscle cells and plays a role in fine-tuning smooth muscle contractility. Calponin 2 is expressed in both smooth muscle and non-muscle cells and regulates multiple actin cytoskeleton-based functions. Calponin 3 participates in actin cytoskeleton-based activities in embryonic development and myogenesis. Phosphorylation has been extensively studied for the regulation of calponin functions. Cytoskeleton tension regulates the transcription of CNN2 gene and the degradation of calponin 2 protein. This review summarizes our knowledge learned from studies over the past three decades, focusing on the evolutionary lineage of calponin isoform genes, their tissue- and cell type-specific expressions, structure-function relationships, and mechanoregulation.

Early inhibition of EGFR signaling prevents diabetes-induced up-regulation of multiple gene pathways in the mesenteric vasculature

Diabetes mellitus is associated with vascular complications including an impairment of vascular function and alterations in the reactivity of blood vessels to vasoactive hormones. However, the signaling mechanisms leading to vascular dysfunction in diabetes are not fully understood. This microarray-based study was designed to identify differential gene expression between the normal and diabetic mesenteric vasculature and to investigate the effect of inhibiting epidermal growth factor receptor (EGFR) signaling on global gene expression in the mesenteric bed of streptozotocin (STZ)-induced diabetic rats. Transcriptome analysis was performed in triplicate using oligonucleotide microarrays housing 10,000 rat genes on the mesenteric bed of normal, diabetic, and diabetic rats treated with AG1478, a selective inhibitor of EGFR. Four weeks of diabetes led to a profound alteration in gene expression within the mesenteric bed with 1167 of the 3074 annotated genes being up-regulated and 141 genes down-regulated by at least 2-fold. The up-regulated gene ontologies included receptor tyrosine kinases, G-protein coupled receptors and ion channel activity. In particular, significant overexpressions of colipase, phospholipase A2, carboxypeptidases, and receptor tyrosine kinases such as EGFR, erbB2 and fibroblast growth factor receptor were observed in diabetes mesenteric vasculature. A 4-week intraperitoneal treatment of diabetic animals with AG1478 (1.2 mg/kg/alt diem) beginning on the same day as STZ injection prevented up-regulation of the majority (approximately 95%) of the genes associated with STZ diabetes including those apparently "unrelated" to the known EGFR pathway without correction of hyperglycemia. These results suggest that activation of EGFR signaling is a key initiating step that leads to induction of multiple signaling pathways in the development of diabetes-induced vascular dysfunction. Thus, therapeutic targeting of EGFR may represent a novel strategy for the prevention and/or treatment of vascular dysfunction in diabetes.