CDK5 regulates cell-cell and cell-matrix adhesion in human keratinocytes.
BACKGROUND
CDK5 is a member of proline-directed serine/threonine kinases. Although its cDNA was originally cloned as a homologue to those for the other members of the cyclin-dependent kinase (CDK) family, CDK5 has been shown to function differently from other CDKs. CDK5 is activated by non-cyclin partners, p35 and p39, and important during brain development by influencing adhesion, migration and differentiation of neurones.


OBJECTIVE
We sought to investigate the expression and functions of CDK5 in human keratinocytes.


METHODS
Expression of CDK5/p35, interaction of CDK5/p35 with adhesion molecules, and its roles in cell-cell and cell-matrix adhesion were studied by reverse transcriptase-polymerase chain reaction, immunoblotting and aggregation/adhesion assays in primary cultured normal human keratinocytes from infant foreskins and a human keratinocyte HaCaT cell line. Localization of CDK5 and p35 in normal human epidermis and psoriatic epidermis was studied by immunohistochemistry.


RESULTS
Both CDK5 and p35 were expressed in primary cultured keratinocytes, HaCaT cells and normal human epidermis. Roscovitine, an inhibitor of CDK5, enhanced Ca2+-dependent (cadherin-dependent) aggregation of HaCaT cells whereas it inhibited adhesion of HaCaT cells to fibronectin associated with reduced active states of beta1 integrin. Interestingly, psoriatic skin showed reduced CDK5 and p35 expression in the lower half of the epidermis, which might be associated with decreased amount of activated beta1 integrin in the epidermis of psoriatic skin.


CONCLUSIONS
CDK5/p35 may be involved in cell-cell and cell-matrix adhesion in human keratinocytes by differently regulating cadherins and integrins. Furthermore, reduced expression of CDK5/p35 in the epidermis might be involved in the pathogenesis of psoriasis.
Nakano
N
N
Atopy (Allergy) Research Center, Juntendo University School of Medicine, Tokyo, Japan. nbnakano@med.juntendo.ac.jp
Nakao
A
A
Ishidoh
K
K
Tsuboi
R
R
Kominami
E
E
Okumura
K
K
Ogawa
H
H
D002118:Calcium / Q000502:physiology; D002448:Cell Adhesion / Q000502:physiology; D002449:Cell Aggregation / Q000187:drug effects / Q000502:physiology; D021982:Cell-Matrix Junctions / Q000502:physiology*; D002478:Cells, Cultured; D051360:Cyclin-Dependent Kinase 5; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D004817:Epidermis / Q000201:enzymology; D005353:Fibronectins / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D007223:Infant; D019012:Integrin beta1 / Q000378:metabolism; D015603:Keratinocytes / Q000166:cytology / Q000201:enzymology*; D009419:Nerve Tissue Proteins / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011565:Psoriasis / Q000201:enzymology*; D011687:Purines / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D000077546:Roscovitine
D005353:Fibronectins; D019012:Integrin beta1; D009419:Nerve Tissue Proteins; D047428:Protein Kinase Inhibitors; D011687:Purines; D012333:RNA, Messenger; C089495:neuronal Cdk5 activator (p25-p35); D000077546:Roscovitine; D051360:Cyclin-Dependent Kinase 5; C495905:CDK5 protein, human; D018844:Cyclin-Dependent Kinases; D002118:Calcium