Our long-term goal is to better understand signal transduction systems that control airway smooth muscle tone, both in normal and in diseased airways. We have emphasized investigation of inositol phospholipid-phosphate signal transduction. The proposed experiments follow our data and data obtained by others that indicate muscle length controls muscarinic agonist-evoked phosphatidylinositol (PI) turnover. The site of control of PI turnover in the PI cycle and the length or strain sensors that provide signals that control PI turnover are unknown. We will test the postulate that the length-strain sensor that controls PI turnover is a 51 intergrin receptor and study characteristics of this length sensor system. We will test the postulate, supported by our preliminary data, that length effects on PI turnover are effected by controlling phosphatidylinositol 4-kinase-mediated conversion of PI to PI-4-phosphate. We will utilize two preparations: intact muscle and isolated low buoyant density microdomains. Studies in intact muscle are directed to determine relationships of muscle length-dependent 51 integrin inward signaling and muscle length-dependent PI turnover. We will determine if length-dependent CARB-evoked paxillin tyrosine phosphorylation, a measurement of integrin signaling, is dependent on activation of Rho A, if it is inhibited by pretreatment of the muscle with c3 exotoxin, and if this treatment prevents muscle length-dependent CARB-evoked PI turnover. Following our finding that the majority of cellular paxillin is present in cytosol, we will investigate if cytoplasmic paxillin is involved in integrin signaling. Isolating low buoyant density microdomains offers another approach to study how PI turnover can be activated by muscarinic and length signals. We plan to determine if PI turnover channels through these small domains and if PI transfer proteins function in activation of P14Kase in these domanins during length-dependent muscarinic activation of the muscle. Proposed experiments should produce data important to our understanding of the mechanaisms of length-dependent signaling which are relevant to improving our understanding of airway smooth muscle function in vivo. Airway smooth function is markedly altered in many different lung diseases, including asthma, bronchitis and emphysema. In particular, all of these diseases cause physiological alterations that influence the length at which smooth muscle cells contract and relax.
| Moreland, R S; Coburn, R F; Moreland, S (1995) Decreased PO2 and rabbit aortic smooth muscle mechanics. J Vasc Res 32:313-9 |
| Coburn, R F; Mitchell, H; Dey, R D et al. (1994) Capsaicin-sensitive stretch responses in ferret trachealis muscle. J Physiol 475:293-303 |
