Induction of 73-kDa and 90-kDa Heat Shock Protein Expression in HL60 Cells during Differentiation.

Abstract

We investigated the expression of heat shock proteins HSP73 and HSP90 in human promyelocytic line HL60 during their differentiation induced by phorbor ester and all trans retinoic acid (ATRA). Polyclonal antibodies which had been raised against HSPs purified from bovine brains were used to detect human HSPs. Semiquantitation of HSPs was performed by immunoblotting. Induction of monocytoid and granulocytoid differentiation with phorbor ester and ATRA was accompanied by increased expression of HSP73 and HSP90 with distinct kinetics. Increased expression of both HSPs was confirmed by immunocytochemical studies. Our results suggest that HSP73 and HSP90 may be involved in differentiation of HL60 cells.heat shock proteins; HL60 cells; differentiationHeat shock proteins (HSPs) have been described as a family of proteins expressed in not only prokaryotes but eukaryotes whose production is induced by a variety of noxious insults (Hunt and Morimoto 1985;Burdon 1986;Lindquist 1986). It is now clear that HSPs are also present and active in normal cells and serve important physiological functions (Schlesinger 1986;Ellis 1987;Lindquist and Craig 1988). HSPs have been generally defined by their molecular weight: HSP90, HSP70 and low molecular weight HSP families (Schlesinger 1986;Itoh and Tashima 1990). HSP70 consists of two forms of proteins: the stressinducible 72-kDa protein (HSP72), an induced form whose synthesis is most obvious after physiological stress, and the constitutive 73-kDa protein (HSP73, Welch and Framisco 1985), a constitutively present in appreciable levels under normal condition. HSP90 is constitutively present in mammalian cells and