Bulletin Autumn‧Winter 1995

Si gnal T r an s du c t i on i n Mac r ophages Signa l Transductio n Human cells are i nvo l ved i n many activities — they g r ow, they divide, they secrete, and they die. Wh i le biochemists have l ong recognized many of the stimuli that p r ompt these activities, they are on ly n ow beginning to understand h ow a ce ll senses these s t i mu li i n the e x t e r nal environment, and converts t hem into chemical signals that i n turn elicit the appropriate response. Signal transduction refers to the process whe r eby extracellular messengers (i.e., the 'first messengers') such as ho rmones and g r ow th factors, i mp i ng i ng u p on the cell surface, induce changes i n surface molecules called receptors. The cell then produces a 'second messenger', for instance by way of an enzyme, to initiate a cascading series of molecular interactions wh i ch amplify the original signal and transmit them to various parts of the cell to start, modulate and terminate various cellular activities (Fig. 1). A n y u n t o w a rd happen i ngs i n the signal transduction pathways might cause the cell to lose control of its o w n activities, resulting i n v a r i ous types o f diseases i n c l u d i ng loss of i mmu ne function, diabetes and cancer. Prof. C.Y. Lee and Dr. S.K. Ko ng of the Department of Biochemistry at CUHK began w o r k o n signal transduction i n 1987. The ir research efforts have w o n continuous financial support f r om the University Grants Committee i n previous years, and they have now. been awarded a competitive grant of HK$1,291,000 by the Research Grants Council for a pe r i od of t wo years (1st October 1994 to 31st September 1996) for their study o n macrophages. The Macrophag e as th Focu s of Researc h The macrophage is a wh i te b l o od cell whose p r i ma ry f u n c t i on is to h e lp the b o dy f i ght infectious agents. It does so by either gobb l i ng up the bacteria (phagocytosis) or by secreting products wh i ch possess the potential to destroy bacteria and cancer cells. The macrophage also i den t i f i es d i sease - caus i ng agents to o t h er immune cells, and thus stimulates the latter to battle. It hence plays a crucial role in our first-line defence mechanism as we ll as specific immunity, and it is this that makes it so vital a focal po i nt for researchers (Fig. 2). Curren t Researc h Effort s The overall aim of Prof. Lee and Dr. Ko ng is to examine the cellular mechanisms w h i ch gove rn macrophage development, activation and cell death. I n their previous wo r k they have identified a number of extracellular stimuli w h i ch induce ma c r o p h a ge activities, a nd have r e c o r d ed Fig. 1 Signal transduction in macrophages Fig. 2 Macrophage Research 21