SUBCELLULAR-DISTRIBUTION AND DIFFERENTIAL EXPRESSION OF ENDOGENOUS ADP-RIBOSYLATION FACTOR-6 IN MAMMALIAN-CELLS

ADP-ribosylation factor (ARF) 6 has been shown to play a role in vesic ular transport; however, the expression and subcellular localization o f the endogenous protein have not been clearly delineated, In this stu dy, an ARF6-specific monoclonal antibody was raised and used to examin e the subcellular distribution and expression of ARF6 in various tissu es and during the differentiation of several well characterized cell t ypes, We found that ARF6 localizes in both the cytosol and membranes o f all tissues and cells tested, Moreover, ARF6 in 3T3-L1 adipocytes is principally localized on the plasma membrane, but substantial amounts are detected in the cytosolic and intracellular membrane fractions, W e observed an increased expression of ARF6 during the differentiation of B lymphocytes to plasmocytes, However, the expression of ARF6 decre ased during adipogenesis and monocyte differentiation. In contrast, th e expression of other ARFs, detected by the monoclonal antibody 1D9, d id not significantly change during differentiation of the aforemention ed cell types, Taken together, our results indicate that ARF6 is a bro adly expressed, differentially regulated GTPase that is present in cyt oplasm and on both cell-surface and intracellular membranes and whose functions may include tissue-specific effects on vesicular trafficking during cellular differentiation.