I. Kindasmugge et F. Trautinger, INCREASED EXPRESSION OF THE M(R) 27,000 HEAT-SHOCK PROTEIN (HSP27) ININ-VITRO DIFFERENTIATED NORMAL HUMAN KERATINOCYTES, Cell growth & differentiation, 5(7), 1994, pp. 777-781
The M(r) 27,000 heat shock protein (hsp27) is a member of the small he
at shock protein family. Cell differentiation is a process in which a
role for small heat shock proteins has been suggested. The ability to
control the state of differentiation in normal human keratinocytes by
modification of extracellular calcium concentration makes it an ideal
in vitro system for exploration of the specific components and steps i
n differentiation. We have focused on the in vitro expression of hsp27
in undifferentiated and differentiated human normal keratinocytes (HN
K) as a marker for differentiation. Immunological methods (immunohisto
chemistry and immunoblotting) as well as Northern blotting were used.
Cells of the breast cancer line MCF-7 served as a positive control. We
demonstrated that hsp27 was expressed at low levels in normal human k
eratinocytes, kept under calcium concentrations where cells formed dis
crete colonies of undifferentiated, noncornified cuboidal cells (0.03
mM Ca2+), and linked cuboidal cells with a noncornified appearance (0.
15 mM Ca2+). Upon cultivation in high calcium (1.00 mM Ca2+) where a m
ore morphological state of differentiation was reached, more spindle s
haped with cornification of individual cells, a 2-fold increase in hsp
27 expression was observed. A somewhat weaker increase in hsp27 mRNA w
as shown by Northern blot analysis. Our studies provide evidence that
hsp27 is accumulated in a differentiation-dependent manner in human no
rmal keratinocytes grown under conditions inducing terminal differenti
ation (0.03-1.00 mM Ca2+). Therefore, hsp27 can be regarded as a marke
r of differentiation in human normal keratinocytes.