Complementary roles of specific cysteines in keratin 14 towards the assembly, organization, and dynamics of intermediate filaments in skin keratinocytes [Cell Biology]
July 27th, 2015 by Feng, X., Coulombe, P. A.
We recently showed that inter-keratin disulfide bonding plays an important role in the assembly, organization, and dynamics of keratin intermediate filaments in skin keratinocytes. In particular, cysteine 367 (C367) located in the central alpha-helical rod domain of keratin 14 is necessary for the formation of a stable perinuclear network of keratin filaments (with type II partner keratin 5) in skin keratinocytes analyzed by static and live cell imaging. Here, we show that two additional cysteine residues located in the non-helical head domain of K14, C4 and C40, also participate in inter-keratin disulfide bonding and tandemly play a key and complementary role to that of C367 towards the assembly, organization and dynamics of keratin filaments in skin keratinocytes in primary culture. Analysis of K14 variants with single or multiple substitutions of cysteine residues points to a spatial and temporal hierarchy in how C4/C40 and C367 regulate keratin assembly in vitro and filament dynamics in live keratinocytes in culture. Our findings substantiate the importance and complexity of a novel determinant, namely inter-keratin disulfide bonding, towards the regulation of several aspects of keratin filaments in surface epithelia.