Stimulus-induced translocation of the protein kinase A catalytic subunit to the apical membrane in blowfly salivary glands

Abstract

Secretion in blowfly (Calliphora vicina) salivary glands is regulated by the neurohormone serotonin (5-HT), which activates the InsP(3)/Ca(2+) pathway and the cAMP/protein kinase A (PKA) pathway in the secretory cells. The latter signaling cascade induces the activation of a vacuolar H(+)-ATPase on the apical membrane. Here, we have determined the distribution of PKA by using antibodies against the PKA regulatory subunit-II (PKA-RII) and the PKA catalytic subunit (PKA-C) of Drosophila. PKA is present in high concentrations within the secretory cells. PKA-RII and PKA-C co-distribute in non-stimulated glands, being enriched in the basal portion of the secretory cells. Exposure to 8-CPT-cAMP or 5-HT induces the translocation of PKA-C to the apical membrane, whereas the PKA-RII distribution remains unchanged. The recruitment of PKA-C to the apical membrane corroborates our hypothesis that vacuolar H(+)-ATPase, which is enriched in this membrane domain, is a target protein for PKA.

Development of apical membrane organization and V-ATPase regulation in blowfly salivary glands

“…To determine whether developmental differences exist in the ability of secretory cells to assemble V 1 V 0 holoenzymes in a cAMP-dependent mode, we first determined the developmental expression pattern of the catalytic (PKA-C) and regulatory (PKA-RII) subunit of PKA. Fig.4 demonstrates that PKA-RII and the major PKA-C isoform expressed in the salivary glands, namely PKA-C1 corresponding to the intense 41kDa band on the anti-PKA-C blot (Voss et al, 2009), were expressed at a similar level in newly eclosed salivary glands and at latter developmental stages.…”

“…Cross-reactivity of these antibodies with the homologous proteins in C. vicina has been demonstrated previously (Zimmermann et al, 2003;Dames et al, 2006;Voss et al, 2007;Voss et al, 2009;Baumann and Walz, 2012). Monoclonal anti-actin (clone C4) was obtained from Merck (Darmstadt, Germany), rabbit antiserum (cat.…”

The Ras/cAMP/Protein Kinase A Pathway Regulates Glucose-dependent Assembly of the Vacuolar (H+)-ATPase in Yeast

“…This effect is blocked by PKA inhibitors. In addition, the catalytic (but not regulatory) subunit of PKA translocates to the apical membrane when these cells are treated with the cAMP analog 8-CPT-cAMP (52). Interestingly, phosphorylation of the V-ATPase C subunit by PKA also occurs concomitant with these translocation events (24).…”

The N-terminal domain of the V-ATPase subunit 'a' is regulated by pH in vitro and in vivo

“…8, [10][11][12][13][14][15] Interestingly, V-ATPase has been shown to interact with a downstream effector, the Rab-GEF ARNO, in an activity-dependent manner. 16 Based on this work, it has been suggested that V-ATPases themselves act as pH sensors.…”