Smooth Myocytes - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 384

Tabl e 8. 2. Calponin-binding proteins (Source: [ 710 ]). Addition of calponin to actin-tropomyosin
complex provokes formation of actin bundles.

Partner Function

Actin Modulation of actin-myosin-2 ATPase activity

α -Actinin Stabilization of the α -actinin-actin complex

Caldesmon Myosin-2 binding regulation

Caltropin Weakening of caldesmon-actin interaction

Calmodulin Inhibition of actin binding

Myosin-2 Stimulation of myosin-2 ATPase activity

Tropomyosin Actin stability and myosin-2 regulation

Tubulin Microtubule binding

HSP90 Prevention of actin bundle formation

Decrease in calponin-induced polymerization of G actin

CamK2 Phosphorylated

ERK1/2 Scaffolding for ERK signaling

PKC Phosphorylated

Interstitial flow upregulates matrix metalloproteinase expression in rat vascular
smooth myocytes, fibroblasts, and myofibroblasts via the FAK-ERK1/2-Jun path-
way [ 712 ]. At the surface glycocalyx of rat vascular smooth myocytes, heparan
sulfate proteoglycans sense interstitial flow and transduce this mechanical signal.
Subsequent phosphorylated (activated) of mechanosensitive focal adhesion kinase
enable ERK1/2 activation, interstitial collagenase (MMP13) expression, and smooth
myocyte motility.

8.3 Intrinsic Regulators of Smooth Myocyte Tone

8.3.1 Caldesmon and Calmodulin

Caldesmon may act on F actin by either phosphorylation by protein kinase-C and
Ca 2 + or formation of a caldesmon-calcium-calmodulin complex that is unable
to bind to actin. Moreover, caldesmon enhances the binding of ATP-bound heavy
meromyosin (HMM), as well as (but to a lesser extent) the subfragment S1-ATP
(like HMM-ATP in skeletal myocytes), to actin [ 713 ]. This effect is hindered by
Ca 2 + -calmodulin. Caldesmon also interacts with myosin in a process regulated by
casein kinase-2 [ 714 ].