Smooth muscle phenotype may be modulated in response to external conditions under physiologic and pathophysiologic conditions. Mechanical stress and humoral stimuli may activate signaling pathways that regulate changes in smooth muscle phenotype via cytoskeletal signaling pathways activated by integrin proteins. Integrin linked kinase (ILK) is a multidomain protein kinase that binds to the cytoplasmic domain of β integrins and forms a heterotrimeric complex with the adaptor protein, PINCH, and with α-parvin: the ILK/PINCH/parvin (IPP) complex. Alpha-parvin binds to actin filaments; thus the IPP complex can link integrins to the actin cytoskeleton. The IPP complex is maintained as a stable complex in the cytoplasm of tracheal muscle tissues and is recruited to adhesion junctions in response to contractile stimulation, where it mediates ACh-induced actin polymerization (Zhang et al, J. Biol. Chem, 2007). In tracheal smooth muscle, ILK modulates the expression of smooth muscle specific marker proteins by regulating the activity of Akt; Akt activation suppresses SRF binding to the promoters of smooth muscle specific genes and suppresses the expression of smooth muscle marker proteins (Wu et al. Am J Physiol Lung Cell Mol Physiol, 2008). The effects of mechanical stimuli on tracheal smooth muscle phenotype were evaluated in vitro by suspending low or high loads (0.5 gm or 1 gm) from smooth muscle tissues, incubating the weighted tissues for 6 hours, and then measuring the expression of smooth muscle myosin heavy chain (SmMHC) and Akt activation. In muscles subjected to the higher load, expression of SmMHC increased and Akt activation was suppressed relative to tissues subjected to the lower load. The role of the IPP complex in regulating Akt activation and the expression of SmMHC protein in response to mechanical stimulation was evaluated. Mutant constructs for the PINCH LIM1-2 peptide, which inhibits recruitment of the IPP complex, kinase inactive ILK (ILK S343A), or kinase inactive Akt (T308A, S473A) were expressed in tracheal muscle tissues. All 3 mutants decreased Akt activation and increased expression of SmMHC protein of tissues incubated at low load but had little effect on SmMHC expression induced by high load. Thus, the localization of the IPP complex to integrin adhesion sites and activation of ILK and Akt suppressed the mechano-sensitivity of SmMHC expression, suggesting that integrin proteins are the primary sensors for mechanical signals that regulate smooth muscle phenotype. Stimulation of tissues with the inflammatory mediator IL-13 activated Akt and inhibited expression of SmMHC, opposing the effects of mechanical load. These effects of IL-13 were suppressed by inhibiting the recruitment of the IPP complex, indicating that the IPP complex recruitment is required for the phenotypic changes induced by IL-13. We conclude that mechanical stimulation maintains the differentiated state of airway smooth muscle via integrin-mediated signaling pathways, and that inflammatory stimuli may suppress the stimulatory effects of mechanical load on the expression of smooth muscle phenotype-specific contractile proteins.