The distribution of protein kinase A regulatory and catalytic subunits varies during development inhte mouse olfactory system.

Poster session I Poster #121 The distribution of protein kinase A regulatory and catalytic subunits varies during development in the mouse olfactory system Carla Mucignat1 and Antonio Caretta2 1University of Padova, Dept. of Molecular Medicine, Padova, Italy 2University of Parma, Dept. of Pharmaceutical Sciences, Parma, Italy carla.mucignat@unipd.it The second messenger cAMP regulates several cellular functions mainly through cAMP-dependent protein kinases (PKA). They are tetramers of two catalytic (C) and two regulatory (R) subunits, of which four isoforms are known: RIalpha, RIbeta, RIIalpha, RIIbeta. PKA distribution inside the brain changes according to cell type, age and physiological status, possibly modifying neuronal responses to variations in cAMP concentration. Therefore, the localization of PKA isoforms was examined during development in the mouse central and peripheral olfactory system, via immunohistochemistry and Western blot. In the peripheral olfactory organs, the olfactory mucosa showed a strong PKA labelling both for R and C subunits. C colocalized with both R subunits. RII was present in the luminal area, while sparse RI aggregates were observed in the inner layers. In the vomeronasal epithelium, only RII and C, but not RI, were detected on the luminal layer. The intensity of labelling increased in the first postnatal week for RII subunits. Like in other brain areas, PKA R subunits were present both in the soluble and in the detergent-insoluble fraction of olfactory bulb. PKA regulatory subunits were variously distributed in the olfactory bulb but never colocalized in the same subcellular structure. In the main olfactory bulb, RIalpha colocalized with C, and showed the main changes during development, being absent at birth, increased in mitral cell layer between postnatally day 5 to 15, and started to decrease at one month of age. A similar time course was detected in the accessory olfactory bulb. In the central olfactory projection areas (bed nucleus of the stria terminalis, olfactory and vomeronasal amygdala and olfactory cortex), RIalpha increased between P15 and P30, declining thereafter. Therefore, the distribution of PKA R and C subunits is modified during development and increases postnatally, in parallel with functional maturation of the olfactory system.