Phosphorylation of the stress protein hsp27 is an early event in murine myelomonocytic leukemic cell differentiation induced by leukemia inhibitory factor/D-factor.
Leukemia inhibitory factor/D-factor, a potent differentiation-inducing glycoprotein for murine myelomonocytic leukemic M1 cells, rapidly stimulated the phosphorylation of a 27 kDa protein with an isoelectric point of 5.6 in a LIF-sensitive M1-T22 cell line but not in a LIF-resistant M1-D(-) cell line. The increase in phosphorylation was detectable 5 min after LIF treatment and was maximal at 10 min. Heat shock treatment at 44.5 degrees C for 30 min also induced the phosphorylation of the same 27 kDa protein. Although this 27 kDa protein did not become labeled with [35S]-methionine, metabolic labeling experiments using [35S]-cysteine or [3H]-leucine clearly demonstrated that the synthesis of this protein was enhanced after heat shock. These results suggest that the phosphorylated 27 kDa protein is a low molecular weight stress protein and that the protein may play a role at an early stage in the LIF signaling pathway probably linked to macrophagic differentiation.
Michishita
M
M
First Division of Internal Medicine, Faculty of Medicine, Kyoto, Japan.
Satoh
M
M
Yamaguchi
M
M
Hirayoshi
K
K
Okuma
M
M
Nagata
K
K
D000818:Animals; D002454:Cell Differentiation; D002460:Cell Line; D003545:Cysteine / Q000378:metabolism; D006131:Growth Inhibitors; D006360:Heat-Shock Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D015850:Interleukin-6; D007700:Kinetics; D007930:Leucine / Q000378:metabolism; D053605:Leukemia Inhibitory Factor; D007942:Leukemia, Experimental / Q000378:metabolism* / Q000473:pathology; D015479:Leukemia, Myelomonocytic, Acute / Q000378:metabolism / Q000473:pathology; D008222:Lymphokines / Q000494:pharmacology*; D008715:Methionine / Q000378:metabolism; D051379:Mice; D010710:Phosphates / Q000378:metabolism; D010766:Phosphorylation
D006131:Growth Inhibitors; D006360:Heat-Shock Proteins; D015850:Interleukin-6; D053605:Leukemia Inhibitory Factor; C507838:Lif protein, mouse; D008222:Lymphokines; D010710:Phosphates; D008715:Methionine; D007930:Leucine; D003545:Cysteine