TI - Signaling pathways used in trabecular matrix metalloproteinase response to mechanical stretch . AB - PURPOSE : Trabecular meshwork ( TM ) matrix metalloproteinase ( MMP ) , and tissue inhibitor ( TIMP ) changes in response to mechanical stretching appear to be central to intraocular pressure ( IOP ) homeostasis . Studies were conducted to define the signal transduction pathway responsible for the increases in MMP-2 and -14 that occur in response to mechanical stretching of TM cells . METHODS : Porcine TM cells were subjected to mechanical stretching , and changes in MMP-2 and -14 levels were determined by gelatin zymography and Western immunoblot analysis . Effects of signal transduction pathway inhibitors on MMP levels were analyzed . Phosphospecific antibodies were used to identify phosphorylation changes in select pathway intermediates . In silico secondary structure analysis was conducted on the 5' untranslated regions ( UTRs ) of MMP-2 and -14 mRNAs . RESULTS : The increases in MMP-2 and -14 that occur 24 hours after sustained mechanical stretching of TM cells were blocked by rapamycin . Wortmannin blocked the MMP-2 but not the MMP-14 increase . Protein kinase B ( PKB ) phosphorylation on S473 and T308 was increased significantly by stretching . Rapamycin-sensitive phosphorylation of T389 in p70/p85 S6 kinase was also increased . The phosphorylations of the translation initiation factor eIF-4E on S209 and of its inhibitory binding protein 4E-BP1 on T70 were both increased by stretch . The calculated free energies of secondary structures of the 5' UTRs of the mRNAs for MMP-2 and -14 were negative and relatively large . MMP-2 also had pyrimidine tracts in the extreme 5' region of its UTR . CONCLUSIONS : The increases in TM MMP-2 and -14 protein levels in response to mechanical stretching appear to be transduced atleast in part by mTOR , the mammalian target of rapamycin ( mTOR ) . The wortmannin sensitivity implicates phosphoinositide 3-kinase as a modulator of the MMP-2 but not the MMP-14 increase . Integrin-linked kinase ( ILK ) , phosphoinositide-dependent kinase ( PDK-1 ) , and PKB are implicated in the MMP-2 increase . Translational initiation involving eIF-4E and its inhibitory binding protein 4E-BP1 appear to be involved in both the MMP-2 and -14 increases with stretching and are normally regulated by mTOR . The high degree of secondary structure in the 5' UTRs of these transcripts is typically an indicator of genes specifically sensitive to regulation through this pathway . P70/p85 S6 kinase is probably involved downstream from mTOR and PKB in regulating translation of MMP-2 , which has pyrimidine tracts in its 5' UTR . Manipulation of these transduction pathways may provide new approaches to therapeutic IOP regulation .