1. Cellular and molecular mechanisms of desensitisation of hormone response

2. The beta-adrenergic signalling cascade in brown adipose tissue                    

3. Na⁺/K⁺-ATPase, receptor for cardiac glycosides. Important experimental results

1. Cellular and molecular mechanisms of desensitisation of hormone response.
Agonist-induced subcellular redistribution of GPCR (G-protein-coupled receptors), agonist-induced subcellular redistribution of trimeric G proteins, soluble (cytosolic) forms of trimeric G proteins, caveolae, detergentresistant membrane domains (DRMs), hormoneinduced changes in composition of DRMs, domainbound versus bulk-membrane phase forms of GPCR and G proteins, structure-function correlation of DRMs. The work is performed on selected cell lines expressing the specific types of GPCR, their cognate G proteins or the fusion proteins between GPCR and GFP (green fluorescent protein) within collaboration with Glasgow University, Scotland, UK (Prof. Graeme Milligan) which is supported by The Wellcome Trust.

2. The beta-adrenergic signalling cascade in brown adipose tissue.
Analysis of beta-adrenergic receptors, G proteins and adenylyl cyclase in plasma membranes of brown adipose tissue; primary cultures of brown adipocytes.

3. Na⁺/K⁺-ATPase, receptor for cardiac glycosides.
Important experimental results
Long-term desensitisation of hormone response is associated with internalisation of heterotrimeric G proteins Gqa/G11( which is separated in time and space from internalisation of their cognate receptors (thyrotropin-releasing hormone receptor) (Drmota at al., 1998, 1999). Thus, internalisation of Gqa/G11( proceeds independently of the TRH receptor. Agon-ist-stimulation of GPCR (G protein coupled receptors) is also associated with subcellular redistribution of their cognate G-protein a subunits which proceeds as transfer from plasma membranes to ensomes (light- or low-density membrane vesicles distinct from plasma membranes) (Svoboda et al. 1992; Svoboda and Milligan 1994; Kvapil et al. 1994; Svoboda et al. 1996) and solubilization, i.e. transfer from the plasma membrane to the cytosol (supernatant at 200 000 ( g) (Ransnas et al. 1989; Svoboda et al. 1996). The specific plasma membrane compartments or domains (caveolae, detergent-resistant membrane fragments) also participate in this process (Pešanová et al. 1999). These results bring new ev-idence in favour of the idea that, besides receptorbased mechanisms of desensitisation such as phos-porylation, sequestration and internalisation which proceeds on a relatively short time-scale (minutes), a new, G protein-related mechanisms of this essential homeostatic mechanism exist.