Date on Master's Thesis/Doctoral Dissertation

1-2021

Document Type

Master's Thesis

Degree Name

M.S.

Department

Pharmacology and Toxicology

Degree Program

Pharmacology and Toxicology, MS

Committee Chair

Nystoriak, Matthew A.

Committee Co-Chair (if applicable)

Bhatnagar, Aruni

Committee Member

Bhatnagar, Aruni

Committee Member

Song, Zhao-hui

Committee Member

Jones, Steven P.

Committee Member

Hill, Bradford G.

Committee Member

LeBlanc, Amanda J.

Abstract

Voltage-gated potassium (Kv) channels control vascular resistance and facilitate the augmentation of myocardial blood flow in response to increases in cardiac workload (i.e., metabolic hyperemia). Native sarcolemmal Kv1 channels in arterial myocytes associate with a heteromeric auxiliary complex consisting of intracellular Kvβ1 and Kvβ2 proteins. The Kvβ proteins differentially regulate the function of heterologously expressed Kv channels, as well as native Kv1 channels in excitable cells of the cardiovascular and nervous systems. The physiological importance of vascular Kvβ proteins in mediating vasodilation remains unknown. In this study, I tested the hypothesis that Kvβ proteins functionally regulate vascular tone in response to an altered pyridine nucleotide redox state. I evaluated ex vivo vasoreactivity of small diameter mesenteric arteries isolated from wild type (WT), mutant mice in which either Kv channel subfamily a member regulatory beta subunits 1 or 2 (Kcnab1 or Kcnab2, respectively) was deleted (i.e., Kvβ1.1-/- and Kvβ2-/-, respectively), transgenic mice in which kcnab1.1 overexpression was induced by addition of doxycycline to the water (SM22α-rtTA: TRE β1) and point mutant mice in which the Kvβ2 subunit was catalytically inactive (Kvβ2Y90F). Loss of Kvβ1.1 or Kvβ2 did not significantly impact vasoconstriction in response to elevated extracellular K+ (60 mM), vi U46619 (thromboxane A2 analogue), or increases in intravascular pressure. Whereas vasodilation in response to application of adenosine (10-6 – 10-4 M) was similar between Kvβ-null and WT groups, vasodilation in response to external L-lactate (5-20 mM), which modifies cellular pyridine nucleotide redox state , was sensitive to inhibition by the Kv1-selective inhibitor psora-4 (500 nM) and was abolished in arteries from Kvβ2-/- mice but not in arteries from Kvβ1-/- mice. Interestingly, arteries from mice in which overexpression of the Kvβ1 subunit (SM22α-rtTA: TRE β1) and point-mutated inactivation of Kvβ2 (Kvβ2Y90F) enzymatic function, similarly abolished vasodilation in response to external L-lactate (5-20 mM). Our results indicate that vascular tone is differentially regulated by Kv1-associated Kvβ proteins, whereby Kvβ2 promotes and Kvβ1.1 opposes lactate induced vasodilation. Additionally, our data signify the importance of the Kvβ-subunit complex composition and enzymatic function in promoting vasodilation in response to an altered pyridine nucleotide redox state.

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