Lily Pounkova

Publications of Lily Pounkova

• Poldip2, a Novel Regulator of Nox4 and Cytoskeletal Integrity in Vascular Smooth Muscle Cells.

  Authors: Alicia N Lyle, Nita N Deshpande, Yoshihiro Taniyama, Bonnie Seidel-Rogol, Lily Pounkova, Pingfeng Du, Christopher Papaharalambus, Bernard Lassegue, Kathy K Griendling

  Circulation research. 08/2009;

  Rationale: NADPH oxidases (Noxs) regulate vascular physiology and contribute to the pathogenesis of vascular disease. In vascular smooth muscle cells (VSMCs), the interactions of individual NoxRationale: NADPH oxidases (Noxs) regulate vascular physiology and contribute to the pathogenesis of vascular disease. In vascular smooth muscle cells (VSMCs), the interactions of individual Nox homologs with regulatory proteins are poorly defined. Objective: The objective of this study was to identify novel NADPH oxidase regulatory proteins. Methods and Results: Using a yeast 2-hybrid screen, we identified a novel binding partner, Poldip2, and demonstrated that it associates with p22phox, NADPH oxidase (Nox)1, and Nox4 and colocalizes with p22phox at sites of Nox4 localization. Poldip2 increases Nox4 enzymatic activity by 3-fold and positively regulates basal reactive oxygen species production in VSMCs (O2(.-): 86.3+/-15.6% increase; H2O2: 40.7+/-4.5% increase). Overexpression of Poldip2 activates Rho (180.2+/-24.8% increase), strengthens focal adhesions, and increases stress fiber formation. These phenotypic changes are blocked by dominant negative Rho. In contrast, depletion of either Poldip2 or Nox4 results in a loss of these structures, which is rescued by adding back active Rho. Cell migration, which requires dynamic cytoskeletal remodeling, is impaired by either excess (70.1+/-14.7% decrease) or insufficient Poldip2 (63.5+/-5.9% decrease). Conclusions: These results suggest that Poldip2 associates with p22phox to activate Nox4, leading to regulation of focal adhesion turnover and VSMC migration, thus linking reactive oxygen species production and cytoskeletal remodeling. Poldip2 may be a novel therapeutic target for vascular pathologies with a significant VSMC migratory component, such as restenosis and atherosclerosis.

• Insulin-Like Growth Factor-1 Receptor Expression Masks the Antiinflammatory and Glucose Uptake Capacity of Insulin in Vascular Smooth Muscle Cells.

  Authors: Niels Engberding, Alejandra San Martín, Abel Martin Garrido, Mitsuhisa Koga, Lily Pounkova, Erin Lyons, Bernard Lassègue, Kathy K Griendling

  Arteriosclerosis, thrombosis, and vascular biology. 02/2009;

  OBJECTIVE: Insulin resistance of vascular smooth muscle cells (VSMCs) has been linked to accelerated atherosclerosis in diabetes; however, the effects of insulin on VSMCs remain controversial. MostOBJECTIVE: Insulin resistance of vascular smooth muscle cells (VSMCs) has been linked to accelerated atherosclerosis in diabetes; however, the effects of insulin on VSMCs remain controversial. Most VSMC insulin receptors are sequestered into insulin-insensitive hybrids with insulin-like growth factor-1 receptors (IGF1R). Thus we hypothesized that regulation of IGF1R expression may impact cellular insulin sensitivity. METHODS AND RESULTS: IGF1R expression was increased in aortas from diabetic mice. IGF1R overexpression in VSMCs impaired insulin-induced Akt phosphorylation. Conversely, IGF1R downregulation by siRNA allowed assembly of insulin holoreceptors, enhanced insulin-induced phosphorylation of its receptor, Akt, Erk1/2, and further augmented insulin-induced glucose uptake. IGF1R downregulation uncovered an insulin-induced reduction in activation of NF-kappaB and inhibition of MCP-1 upregulation in response to TNF-alpha. CONCLUSIONS: Downregulation of IGF1R increases the fraction of insulin receptors organized in holoreceptors, which leads to enhanced insulin signaling and unmasks potential antiinflammatory properties of insulin in VSMCs. Therefore, IGF1R, which is susceptible to feedback regulation by its own ligand, may represent a novel target for interventions designed to treat insulin resistance in the vasculature.

• Nox4 is required for maintenance of the differentiated vascular smooth muscle cell phenotype.

  Authors: Roza E Clempus, Dan Sorescu, Anna E Dikalova, Lily Pounkova, Patricia Jo, George P Sorescu, Harald H H Schmidt, Bernard Lassègue, Kathy K Griendling

  Arteriosclerosis, thrombosis, and vascular biology. 02/2007; 27(1):42-8.

  OBJECTIVE: The mechanisms responsible for maintaining the differentiated phenotype of adult vascular smooth muscle cells (VSMCs) are incompletely understood. Reactive oxygen species (ROS) have beenOBJECTIVE: The mechanisms responsible for maintaining the differentiated phenotype of adult vascular smooth muscle cells (VSMCs) are incompletely understood. Reactive oxygen species (ROS) have been implicated in VSMC differentiation, but the responsible sources are unknown. In this study, we investigated the role of Nox1 and Nox4-derived ROS in this process. METHODS AND RESULTS: Primary VSMCs were used to study the relationship between Nox homologues and differentiation markers such as smooth muscle alpha-actin (SM alpha-actin), smooth muscle myosin heavy chain (SM-MHC), heavy caldesmon, and calponin. We found that Nox4 and differentiation marker genes were downregulated from passage 1 to passage 6 to 12, whereas Nox1 was gradually upregulated. Nox4 co-localized with SM alpha-actin-based stress fibers in differentiated VSMC, and moved into focal adhesions in de-differentiated cells. siRNA against nox4 reduced NADPH-driven superoxide production in serum-deprived VSMCs and downregulated SM-alpha actin, SM-MHC, and calponin, as well as SM-alpha actin stress fibers. Nox1 depletion did not decrease these parameters. CONCLUSIONS: Nox4-derived ROS are critical to the maintenance of the differentiated phenotype of VSMCs. These findings highlight the importance of identifying the specific source of ROS involved in particular cellular functions when designing therapeutic interventions.