As. Menko et Nj. Philip, BETA(1) INTEGRINS IN EPITHELIAL TISSUES - A UNIQUE DISTRIBUTION IN THE LENS, Experimental cell research, 218(2), 1995, pp. 516-521
Integrins have been shown to play a role in directing and maintaining
cell differentiation and polarization. The embryonic lens provides a g
ood system in which to examine their role in epithelial cell different
iation, because ail stages of lens development are represented in an i
ndividual embryonic lens. Therefore, we examined the expression and di
stribution of beta(1) integrin heterodimers in both the lens epitheliu
m and the differentiated lens fiber cells. In lens epithelial cells be
ta(1) integrin was found to be localized to all membrane surfaces. Len
s fiber cells contained beta(1) integrin all along their lateral borde
rs as well as at the site of their attachment to the lens capsule and
at their interface with lens epithelial cells. The distribution of bet
a(1) integrin in the lens was distinct from that observed in simple ep
ithelia, the retinal pigment epithelium (RPE), kidney, and intestine,
where it was limited to a basal lateral localization. We examined the
specific beta(1) integrin heterodimers expressed in the lens by Wester
n blot analysis for the integrin alpha subunits following beta(1) immu
noprecipitation and compared them with those expressed in RPE cells. I
n the lens we detected alpha(3) and alpha(6) subunits but not alpha(1)
, alpha(5), or alpha(V). When the lens was separated into epithelial a
nd fiber cells, we found that alpha(3) was expressed at a higher level
in the epithelial cells, while alpha(6) was primarily associated with
the fiber cells. In the RPE the primary beta(1) integrin detected was
alpha(3). Unlike in lens and kidney, alpha(6) beta(1) integrin in RPE
cells was expressed only at a low level. alpha(V) was also expressed
in RPE cells but not as a beta(1) heterodimer. As in the lens, neither
alpha(5) beta(1) nor alpha(1) beta(1) integrin was detected in RPE Bo
th lens and RPE cells express a specific subset of beta(1) integrin he
terodimers which are likely to be important to the initiation and main
tenance of their differentiated phenotype. (C) 1995 Academic Press, In
c.