zum Inhalt springen

Regulation of contractile activity of cerebral blood vessels and visceral smooth muscle  during development and aging

Smooth muscle cells form the wall of blood vessels and visceral hollow organs such as the gastrointestinal tract. Disturbances of contraction and relaxation underlie a number of severe diseases such as hypertension or sepsis associated hypertension, asthma, and premature labor. Such disease but also development and aging have a profound effect of the protein phenotype of the contractile apparatus leading to concomitant changes in the contractile properties. For instance, smooth muscle cells in atherosclerotic vessels adopt an immature synthetic phenotype.


Smooth muscle contraction is dually regulated. The major activating regulatory mechanisms involves the Ca2+-dependent activation of myosin light chain kinase (MLCK) followed by phosphorylation of the regulatory light chains of myosin (MLC20) while dephosphorylation of MLC20 by a specific phosphatase (MLCP) lowers tone. MLCP is a heterotrimeric enzyme consisting of a catalytic, regulatory subunit, called MYPT1, which targets the catalytic subunit to myosin, and a 20kDa subunit of unknown function. MLCP is itself target of a number of protein kinase cascades that modulate its activity thereby increasing Ca2+-sensitivity of contraction by the Rho/Rho-Kinase and the PKC pathways and decreasing by the cAMP/PKA and cGMP/PKG pathways. These modulatory effects are mediated by phosphorylating several serine and threonine residues on MYPT1 and of regulatory peptides, CPI1, which inhibits MLCP and telokin, thought to activate MLCP. The second regulatory mechanism is thin filament filament based and involves caldesmon and regulation of actin filament stability. However, the precise mechanisms of cyclic nucleotide medatiated relaxation and the role of thin filament linked mechanisms are still incompletely understood.


We have a long standing interest in elucidating the mechanisms that mediate cyclic nucleotide induced desensitization of the contractile machinery to the activator Ca2+ thereby inducing relaxation. These second messengers are generated in response to β-adrenergic stimulation or endothelial NO release. We also investigate the role of the thin filament linked protein, caldesmon, putative regulatory affects smooth muscle function as well as how dedifferentiation of smooth muscle cells is prevented. 

The relative contribution of these pathways to tone regulation differs between different types of smooth muscle and between fetal/neonatal, adult, and aged smooth muscles and between the synthetic/proliferative and contractile phenotype. To elucidate the interplay of these different regulatory pathways we use different gene-modified animals and investigate the biomechanical properties ex vivo of the different intact and permeabilized smooth muscles in conjunction with phosphorylation determinations of the regulatory proteins.  


Selected references:


Eifinger F, Lubomirov LT, Dercks E, Genchev B, Roth B, Neiss WF, et al. Neonatal mouse ileum: functional properties and protein composition of the contractile machinery. Pediatr Res. 2014;76:252-60.

Schroeter MM, Orlova A, Egelman EH, Beall B, Chalovich JM. Organization of F-actin by Fesselin (avian smooth muscle synaptopodin 2). Biochemistry. 2013 Jul 23;52(29):4955-61

Gaynullina D, Lubomirov LT, Sofronova SI, Kalenchuk VU, Gloe T, Pfitzer G, et al. Functional remodelling of arterial endothelium during early postnatal development in rats. Cardiovasc Res. 2013;99:612-21.

Puetz S, Schroeter MM, Piechura H, Reimann L, Hunger MS, Lubomirov LT, et al. New insights into myosin phosphorylation during cyclic nucleotide-mediated smooth muscle relaxation. J Muscle Res Cell Motil. 2012;33:471-83.

Chalovich JM, Lutz E, Baxley T, Schroeter MM. Acrylodan-labeled smooth muscle tropomyosin reports differences in the effects of troponin and caldesmon in the transition from the active state to the inactive state. Biochemistry. 2011 Jul 12;50(27):6093-101.

Hamden SS, Schroeter MM, Chalovich JM. Phosphorylation of caldesmon at sites between residues 627 and 642 attenuates inhibitory activity and contributes to a reduction in Ca2+-calmodulin affinity. Biophys J. 2010 Sep 22;99(6):1861-8.

Shcherbakova OV, Serebryanaya DV, Postnikov AB, Schroeter MM, Zittrich S, Noegel AA, et al. Kinase-related protein/telokin inhibits Ca2+-independent contraction in Triton-skinned guinea pig taenia coli. Biochem J. 2010;429:291-302.

Puetz S, Lubomirov LT, Pfitzer G. Regulation of smooth muscle contraction by small GTPases. Physiology (Bethesda). 2009;24:342-56.

Renegar RH, Chalovich JM, Leinweber BD, Zary JT, Schroeter MM. Localization of the actin-binding protein fesselin in chicken smooth muscle. Histochem Cell Biol. 2009 Feb;131(2):191-6

Neppl RL, Lubomirov LT, Momotani K, Pfitzer G, Eto M, Somlyo AV. Thromboxane A2-induced bi-directional regulation of cerebral arterial tone. J Biol Chem. 2009;284:6348-60.

Schroeter MM, Beall B, Heid HW, Chalovich JM. The actin binding protein, fesselin, is a member of the synaptopodin family. Biochem Biophys Res Commun. 2008 Jul 4;371(3):582-6.

Wenzel D, Schmidt A, Reimann K, Hescheler J, Pfitzer G, Bloch W, et al. Endostatin, the proteolytic fragment of collagen XVIII, induces vasorelaxation. Circ Res. 2006;98:1203-11.

Lubomirov LT, Reimann K, Metzler D, Hasse V, Stehle R, Ito M, et al. Urocortin-induced decrease in Ca2+ sensitivity of contraction in mouse tail arteries is attributable to cAMP-dependent dephosphorylation of MYPT1 and activation of myosin light chain phosphatase. Circ Res. 2006;98:1159-67.

Pfitzer G, Schroeter M, Hasse V, Ma J, Rosgen KH, Rosgen S, et al. Is myosin phosphorylation sufficient to regulate smooth muscle contraction? Adv Exp Med Biol. 2005;565:319-28.

Schroeter MM, Chalovich JM. Fesselin binds to actin and myosin and inhibits actin-activated ATPase activity. J Muscle Res Cell Motil. 2005;26(4-5):183-9.

 Wirth A, Schroeter M, Kock-Hauser C, Manser E, Chalovich JM, De Lanerolle P, et al. Inhibition of contraction and myosin light chain phosphorylation in guinea-pig smooth muscle by p21-activated kinase 1. J Physiol. 2003;549:489-500.

Pfitzer G, Sonntag-Bensch D, Brkic-Koric D. Thiophosphorylation-induced Ca(2+) sensitization of guinea-pig ileum contractility is not mediated by Rho-associated kinase. J Physiol. 2001;533:651-64.

Pfitzer G. Invited review: regulation of myosin phosphorylation in smooth muscle. J Appl Physiol (1985). 2001;91:497-503.

Arner A, Pfitzer G. Regulation of cross-bridge cycling by Ca2+ in smooth muscle. Rev Physiol Biochem Pharmacol. 1999;134:63-146.

Lucius C, Arner A, Steusloff A, Troschka M, Hofmann F, Aktories K, et al. Clostridium difficile toxin B inhibits carbachol-induced force and myosin light chain phosphorylation in guinea-pig smooth muscle: role of Rho proteins. J Physiol. 1998;506 ( Pt 1):83-93.

Katoch SS, Ruegg JC, Pfitzer G. Differential effects of a K+ channel agonist and Ca2+ antagonists on myosin light chain phosphorylation in relaxation of endothelin-1-contracted tracheal smooth muscle. Pflugers Arch. 1997;433:472-7.

Albrecht K, Schneider A, Liebetrau C, Ruegg JC, Pfitzer G. Exogenous caldesmon promotes relaxation of guinea-pig skinned taenia coli smooth muscles: inhibition of cooperative reattachment of latch bridges? Pflugers Arch. 1997;434:534-42.

Otto B, Steusloff A, Just I, Aktories K, Pfitzer G. Role of Rho proteins in carbachol-induced contractions in intact and permeabilized guinea-pig intestinal smooth muscle. J Physiol. 1996;496 ( Pt 2):317-29.

Steusloff A, Paul E, Semenchuk LA, Di Salvo J, Pfitzer G. Modulation of Ca2+ sensitivity in smooth muscle by genistein and protein tyrosine phosphorylation. Arch Biochem Biophys. 1995;320:236-42.

Schmidt US, Troschka M, Pfitzer G. The variable coupling between force and myosin light chain phosphorylation in Triton-skinned chicken gizzard fibre bundles: role of myosin light chain phosphatase. Pflugers Arch. 1995;429:708-15.

Satoh S, Kreutz R, Wilm C, Ganten D, Pfitzer G. Augmented agonist-induced Ca(2+)-sensitization of coronary artery contraction in genetically hypertensive rats. Evidence for altered signal transduction in the coronary smooth muscle cells. J Clin Invest. 1994;94:1397-403.

Pfitzer G, Zeugner C, Troschka M, Chalovich JM. Caldesmon and a 20-kDa actin-binding fragment of caldesmon inhibit tension development in skinned gizzard muscle fiber bundles. Proc Natl Acad Sci U S A. 1993;90:5904-8.

Di Salvo J, Steusloff A, Semenchuk L, Satoh S, Kolquist K, Pfitzer G. Tyrosine kinase inhibitors suppress agonist-induced contraction in smooth muscle. Biochem Biophys Res Commun. 1993;190:968-74.

Boels PJ, Pfitzer G. Relaxant effect of phalloidin on Triton-skinned microvascular and other smooth muscle preparations. J Muscle Res Cell Motil. 1992;13:71-80.

Pfitzer G, Merkel L, Ruegg JC, Hofmann F. Cyclic GMP-dependent protein kinase relaxes skinned fibers from guinea pig taenia coli but not from chicken gizzard. Pflugers Arch. 1986;407:87-91.