Importance of Sugar Chains in the Function of Growth Factor Receptors

Abstract

Growth of normal cells in our body is strictly controlled on demand, and proceeds, e.g., under conditions of wound healing and recovery from inflammation of tissues. Usually, normal cells do not freely grow without appropriate external signals. Such signals are often mediated by proteins known as growth factors. Although these proteins cannot translocate across the plasma membrane, integral membrane receptor proteins receive the extracellular signals through binding growth factors and transmit the signal of growth into the intracellular space. Many receptor proteins are glycosylated, and the addition of sugar chains appears to confer expression of functional receptors. If the receptors do not correctly trigger transmembrane signaling, the proteins may instead activate the intracellular signaling pathways, in spite of the absence of an extracellular signal, causing abnormal cell growth. Thus, loss of normal receptor function could lead to a malignant alteration of cells.