Outer dense fibers serve as a functional target for Cdk5.p35 in the developing sperm tail.
Cdk5 is ubiquitously expressed in all tissues, but its activators, p35 and p39, are principally found in brain, and Cdk5 activity has mostly been associated with brain development, particularly neuronal differentiation and migration. Here we show that the p35 transcript and protein are also present in the testis, and an active Cdk5.p35 complex exists in this tissue as well. Cdk5 and p35 are prominently observed in elongating spermatid tails, particularly over the tail outer dense fibers (ODF). The appearance of Cdk5.p35 proceeds from the proximal to the distal end of elongating spermatids, coinciding with the proximal to distal assembly of ODF along the length of the tail axoneme. Incidentally, increased Cdk5.p35 activity is observed in isolated elongating spermatids and at a time when elongating spermatids appear in the developing testis, suggesting a role for Cdk5.p35 in spermiogenesis. The presence of Cdk5 and p35 in ODF isolated from rat sperm tails implies a strong association among these proteins. In vitro ODF phosphorylation by Cdk5.p35 and decreased in vivo sperm tail ODF phosphorylation in p35-deficient mice indicate that Cdk5.p35 is an integral component of ODF and that ODF is a functional Cdk5.p35 target in the testis. Our results demonstrate for the first time that Cdk5.p35 may participate in the regulation of sperm tail development via a mechanism involving ODF phosphorylation. Apparently, as in brain development, Cdk5.p35 plays a part in testis development.
Department of Cell Biology and Anatomy, The University of Calgary, Calgary, Alberta T2N 4N1, Canada.
Jesusa L
JL
Rosales
Byung-Chul
BC
Lee
Mohammad
M
Modarressi
Krishna P
KP
Sarker
Kyoung-Youl
KY
Lee
Young-Gil
YG
Jeong
Richard
R
Oko
Ki-Young
KY
Lee
D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism; D002454:Cell Differentiation; D004591:Electrophoresis, Polyacrylamide Gel; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008854:Microscopy, Electron; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013082:Sperm Tail / Q000378:metabolism*; D013087:Spermatids / Q000378:metabolism; D013094:Spermatozoa / Q000378:metabolism; D013737:Testis / Q000378:metabolism
C108298:Cdk5 activator p39; D009419:Nerve Tissue Proteins; C089495:neuronal Cdk5 activator (p25-p35); D011494:Protein Kinases; C102333:histone H1 kinase