Skip to Content
MilliporeSigma
  • Defective autophagy in vascular smooth muscle cells alters contractility and Ca²⁺ homeostasis in mice.

Defective autophagy in vascular smooth muscle cells alters contractility and Ca²⁺ homeostasis in mice.

American journal of physiology. Heart and circulatory physiology (2015-01-13)
Cédéric F Michiels, Paul Fransen, Dorien G De Munck, Guido R Y De Meyer, Wim Martinet
ABSTRACT

Autophagy is an evolutionary preserved process that prevents the accumulation of unwanted cytosolic material through the formation of autophagosomes. Although autophagy has been extensively studied to understand its function in normal physiology, the role of vascular smooth muscle (SM) cell (VSMC) autophagy in Ca(2+) mobilization and contraction remains poorly understood. Recent evidence shows that autophagy is involved in controlling contractile function and Ca(2+) homeostasis in certain cell types. Therefore, autophagy might also regulate contractile capacity and Ca(2+)-mobilizing pathways in VSMCs. Contractility (organ chambers) and Ca(2+) homeostasis (myograph) were investigated in aortic segments of 3.5-mo-old mice containing a SM cell-specific deletion of autophagy-related 7 (Atg7; Atg7(fl/fl) SM22α-Cre(+) mice) and in segments of corresponding control mice (Atg7(+/+) SM22α-Cre(+)). Our results indicate that voltage-gated Ca(2+) channels (VGCCs) of Atg7(fl/fl) SM22α-Cre(+) VSMCs were more sensitive to depolarization, independent of changes in resting membrane potential. Contractions elicited with K(+) (50 mM) or the VGCC agonist BAY K8644 (100 nM) were significantly higher due to increased VGCC expression and activity. Interestingly, the sarcoplasmic reticulum of Atg7(fl/fl) SM22α-Cre(+) VSMCs was enlarged, which, combined with increased sarco(endo)plasmic reticulum Ca(2+)-ATPase 2 expression and higher store-operated Ca(2+) entry, promoted inositol 1,4,5-trisphosphate-mediated contractions of Atg7(fl/fl) SM22α-Cre(+) segments and maximized the Ca(2+) storing capacity of the sarcoplasmic reticulum. Moreover, decreased plasma membrane Ca(2+)-ATPase expression in Atg7(fl/fl) SM22α-Cre(+) VSMCs hampered Ca(2+) extrusion to the extracellular environment. Overall, our study indicates that defective autophagy in VSMCs leads to an imbalance between Ca(2+) release/influx and Ca(2+) reuptake/extrusion, resulting in higher basal Ca(2+) concentrations and significant effects on vascular reactivity.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Anti-ATG7 antibody produced in rabbit, affinity isolated antibody, buffered aqueous solution
Sigma-Aldrich
Monoclonal Anti-Actin, α-Smooth Muscle, clone 1A4, ascites fluid
Sigma-Aldrich
Monoclonal Anti-β-Actin antibody produced in mouse, clone AC-15, ascites fluid
Sigma-Aldrich
Anti-p62/SQSTM1 antibody produced in rabbit, ~1 mg/mL, affinity isolated antibody, buffered aqueous solution
Sigma-Aldrich
Anti-Calnexin antibody produced in rabbit, IgG fraction of antiserum, buffered aqueous solution
Sigma-Aldrich
Anti-Calreticulin antibody produced in rabbit, IgG fraction of antiserum, buffered aqueous solution