Details

Autor(en) / Beteiligte

• Zhao, Yu (Joy)

Titel

The regulatory role of ERK1/2 in calcium 2+ ion-dependent and noncalcium 2+ ion-dependent contraction

Ort / Verlag

ProQuest Dissertations & Theses

Erscheinungsjahr

2004

Quelle

ProQuest Dissertations & Theses A&I

Beschreibungen/Notizen

• Accumulating evidence suggests that extracellular signal-regulated kinases (ERK1/2) play a key role in regulating vascular tone. In the present study, we first tested the hypothesis that ERK1/2 play an important role in modulating agonist-induced, α-adrenergic-mediated contraction and [Ca 2+]i responses. In addition, the goal was to determine the extent to which these responses differ in the developing fetus, as compared to the adult. Our results showed that in the fetus, but not adult, inhibition of ERK1/2 increased PHE-induced contraction. In adult and fetal cerebral arteries basal total ERK1/2 levels were similar. However, in fetal arteries the basal phosphorylated ERK1/2 levels were significantly less than in adult. In fetal, but not adult, cerebral arteries, PHE increased ERK1/2 phosphorylation in a dose- and time-dependent manner. In both age groups, ERK1/2 inhibition (U-0126) decreased the PHE-induced [Ca2+]i increase. The present studies suggest that ERK1/2 regulate vascular contractility via mediating myofilament Ca2+ sensitivity. Our data also suggest that ERK1/2 play a more prominent role in fetal vessel contraction regulation than in the adult, and there may be a developmental switch from the regulation of tension by that of myofilament Ca2+ sensitivity in the fetus to Ca2+ concentration in the adult. We also tested the hypothesis that ERK1/2 play an significant role in regulating PKC-induced contraction via mediating MLC20 phosphorylation and caldesmon phosphorylation, thus the actin-myosin ATPase activity. We demonstrated that in adult cerebral arteries, inhibition of ERK1/2, further increased PDBu-induced contraction with no change in [Ca2+]i. We also showed that PKC stimulation can phophorylate ERK1/2, and this leads to phosphorylation of a ERK1/2-specific site on caldesmon (CaDser789). CaD ser789 phsophorylation however, was not required for PDBu-induced contraction. In addition, we demonstrated that PKC activation can phsophorylate CPI-17, which in turn, by inhibiting MLCP activity enhanced MLC20 phsophorylation. This regulatory pathway was ERK1/2-independent. The present studies thus suggest that ERK1/2 play a role in mediating PKC-induced contraction by regulating ERK1/2-specific CaD phosphorylation in thin filament regulation. PKC-induced contraction can also be regulated by increasing calcium sensitivity via the regulation of CPI-17 and MLCP activity. However, ERK1/2 did not appear to play a significant role in this signal transduction pathway. In addition, we studied the contraction-related functions of cytoskeleton protein actin and tubulin cerebral arteries from immature fetus, mature fetus, newborn, and adult. Our data suggested that actin polymerization is critical in agonist-induced contraction. However, unlike the rat pulmonary arteries, tubulin polymerization played no significant role in the regulation of cerebral artery contraction. These data also supported the idea that the signal transduction pathway of regulation of vascular contraction is highly species and tissue specific.