Selective down-regulation of the G(q)alpha/G(11)alpha G-protein family in tumour necrosis factor-alpha induced cell death

Investigations into the regulation of heterotrimeric GTP-binding protein al pha-subunits in models of tumour necrosis factor-alpha (TNF)-induced cell d eath, revealed the selective down-regulation of the G(q)alpha/G(11)alpha fa mily of G-proteins. The human HeLa and murine L929 cells treated with recom binant human TNF for up to 24 h displayed down-regulated G(q)alpha/G(11)alp ha family protein levels, but not G(s)alpha, G(i)alpha and G(o)alpha protei n levels as determined by Western analyses. This effect of TNF was observed in a concentration - and time-dependent manner, consistent with the profil es of TNF-induced cell death observed. Moreover, the functioning of G(q)alp ha/G(11)alpha family proteins were found to be impaired in TNF-treated cell s, as measured by agonist-induced [Ca2+](i) release. In contrast, G(s)alpha activity was unaltered by TNF-treatment, determined by measurement of agon ist-induced intracellular cyclic AMP generation. These findings in TNF-indu ced cytotoxic models, indicate a novel 'cross-talk' mechanism by which TNF alters Ca2+-signalling mechanisms, which may contribute towards the apoptot ic and necrotic cell death.