The objective of this project is to understand the role of HSP27 in normal physiologic mechanisms that modulate smooth muscle contraction of the colon. The investigator propose the existence of an intracellular signaling cascade in colonic smooth muscle that results in the phosphorylation of HSP27 and the association of HSP27 with other contractile proteins, particularly actin, tropomyosin, myosin and caldesmon, leading to smooth muscle contraction. This cascade is initiated by PKC activation, by PKC translocation to the membrane, leading to activation of MAP kinases. The hypothesis is that HSP27 plays an important role in maintaining cytoskeletal integrity, and cytoskeletal association between the contractile proteins within smooth muscle cells. The applicant's studies will determine how phosphorylation of HSP27 confers association with the contractile proteins, leading to contraction. Emerging data suggest that phosphorylation of HSP27 plays a role in cytoskeletal reorganization by increasing stability and association of the contractile proteins in smooth muscle cells. HSP27 is phosphorylated in response to different contractile agonists like bombesin, endothelin, carbachol and ceramide. Preliminary data also suggest that phosphorylation of HSP27 is accompanied by an increase in the complexing of HSP27 with actin and with tropomyosin. Contraction is also accompanied with a strong colocalization of HSP27 with actin and with tropomyosin. The relaxant neuropeptide VIP and the PKC inhibitor calphostin C cause both an inhibition of contraction and an inhibition of HSP27 phosphorylation, suggesting that phosphorylation of HSP27 and contraction may be related.
The specific aims of this proposal are to: 1) examine the effect of PKC mediated contraction on HSP27 phosphorylation and cytoskeletal reorganization: 2) examine the effect of PKC mediated contraction on the association of HSP27 with actin, and other contractile proteins that are members of the contractile machinery in smooth muscle, namely myosin, caldesmon, and tropomyosin; and 3) examine the effect of altered expression of HSP27 on the association of HSP27 with actin, myosin, caldesmon and tropomyosin in transfected cells and in transgenic mice.
| Raghavan, Shreya; Lam, Mai T; Foster, Lesley L et al. (2010) Bioengineered three-dimensional physiological model of colonic longitudinal smooth muscle in vitro. Tissue Eng Part C Methods 16:999-1009 |
| Somara, Sita; Gilmont, Robert R; Varadarajan, Saranyaraajan et al. (2010) Phosphorylated HSP20 modulates the association of thin-filament binding proteins: caldesmon with tropomyosin in colonic smooth muscle. Am J Physiol Gastrointest Liver Physiol 299:G1164-76 |
| Somara, Sita; Gilmont, Robert; Bitar, Khalil N (2009) Role of thin-filament regulatory proteins in relaxation of colonic smooth muscle contraction. Am J Physiol Gastrointest Liver Physiol 297:G958-66 |
| Somara, Sita; Bitar, Khalil N (2008) Direct association of calponin with specific domains of PKC-alpha. Am J Physiol Gastrointest Liver Physiol 295:G1246-54 |
| Somara, Sita; Bitar, Khalil N (2006) Phosphorylated HSP27 modulates the association of phosphorylated caldesmon with tropomyosin in colonic smooth muscle. Am J Physiol Gastrointest Liver Physiol 291:G630-9 |
| Goldsmith, Adam M; Bentley, J Kelley; Zhou, Limei et al. (2006) Transforming growth factor-beta induces airway smooth muscle hypertrophy. Am J Respir Cell Mol Biol 34:247-54 |
| Bitar, Khalil N (2005) Aging and Gi smooth muscle fecal incontinence: Is bioengineering an option. Exp Gerontol 40:643-9 |
| Somara, Sita; Pang, Haiyan; Bitar, Khalil N (2005) Agonist-induced association of tropomyosin with protein kinase Calpha in colonic smooth muscle. Am J Physiol Gastrointest Liver Physiol 288:G268-76 |
| Somara, Sita; Bitar, Khalil N (2004) Tropomyosin interacts with phosphorylated HSP27 in agonist-induced contraction of smooth muscle. Am J Physiol Cell Physiol 286:C1290-301 |
| Bitar, Khalil N; Patil, Suresh B (2004) Aging and gastrointestinal smooth muscle. Mech Ageing Dev 125:907-10 |
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