Two Gq Class G Proteins Are Expressed in Human Keratinocytes

Abstract

G proteins link many cell surface receptor generated signals to activation of multiple cellular processes in all tissues. There is specificity in the receptor interaction with the G protein and in the interaction of the specific G protein with different effector molecules. The purpose of this study was to determine some of the biologically relevant G proteins in keratinocytes. The G alpha subunit of the heterotrimeric G protein was investigated because much of the biologic activity and the receptor specificity resides there. A polymerase chain reaction strategy was used that amplified multiple G alpha gene segments between conserved primer sites from keratinocyte first strand cDNA. Two Gq class G proteins, G alpha 16 and G alpha y, were identified. Using northern analysis and in situ hybridization, mRNA of both of these genes were detected in keratinocytes in culture and in epidermal keratinocytes. G alpha y was expressed in multiple other cell types and tissues, but G alpha 16 was restricted in expression to keratinocytes and keratinocyte-derived adnexal structures in the skin. G alpha 16 has previously been reported to be limited in expression to hematopoietic cells. The physiologic receptor to which it couples in neutrophils is reported to be a C5a receptor. The receptor to which it couples in keratinocytes has not been elucidated but by analogy may be another chemokine receptor. We hypothesize that G alpha 16 is an important conduit for responses to inflammatory signals in keratinocytes.