1alfa, 25(OH)2D3 and PTH signaling in rat intestinal cells: activation of cytosolic PLA2

GENTILI CLAUDIA; MORELLI SUSANA; RUSSO DE BOLAND, ANA

San Carlos de Bariloche

Congreso; XXXIX Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular. (SAIBBM) y XXXII Reunión Anual Sociedad Argentina de Biofisica (SAB); 2003

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular. (SAIBBM) / Sociedad Argentina de Biofisica (SAB)

In the current study, we have probed the role of cytosolicphospholipase A2 (cPLA2) activity in the cellular response to thecalciotropic hormones, 1α25,dihydroxy-vitamin D3 [1α25(OH)2D3]and PTH. Stimulation of rat enterocytes with either hormone,increased release of arachidonic acid [3H-AA] one-two fold in aconcentration and time-dependent manner. The effect of eitherhormone on enterocytes was totally reduced by preincubation withthe intracellular Ca2+ chelator BAPTA-AM (5 μM), suggesting thatthe release of AA following cell exposure to the calciotropichormones occurs mainly through a Ca2+-dependent mechanisminvolving activation of Ca2+-dependent cPLA2. Calciotropichomone stimulation of rat intestinal cells increases cPLA2phosphorylation (3-4 fold). This effect was decreased by PD 98059(20 μM), a MAP kinase inhibitor, indicating that this action is, inpart, mediated through activation of the MAP kinases ERK 1 andERK2. Enterocytes exposure to 1α25(OH)2D3 (1 nM) or PTH (10nM) also resulted in P-cPLA2 translocation from cytosol to nucleiand membrane fractions, where phospholipase subtrates reside.Collectively, these data suggest that PTH and 1α25(OH)2D3 activate in duodenal cells, a Ca2+-dependent cytosolic PLA2 andattendant arachidonic acid release and that this activation requieresprior stimulation of intracellular ERK1/2. 1α,25(OH)2D3 and PTHmodulation of cPLA2 activity may change membrane fluidity andpermeability and thereby affecting intestinal cell membranefunction.TS-C8.