Characterization of organic cation/carnitine transporter family in human sperm.
Spermatozoan maturation, motility, and fertility are, in part, dependent upon the progressive increase in epididymal and spermatozoal carnitine, critical for mitochondrial fatty acid oxidation, as sperm pass from the caput to the cauda of the epididymis. We demonstrate that the organic cation/carnitine transporters, OCTN1, OCTN2, and OCTN3, are expressed in sperm as three distinct proteins with an expected molecular mass of 63 kDa, using Western blot analysis and our transporter-specific antibodies. Carnitine uptake studies in normal control human sperm samples further support the presence of high-affinity (OCTN2) carnitine uptake (K(m) of 3.39+/-1.16 microM; V(max) of 0.23+/-0.14 pmol/min/mg sperm protein; and mean+/-SD; n=12), intermediate-affinity (OCTN3) carnitine uptake (K(m) of 25.9+/-14.7 microM; V(max) of 1.49+/-1.03 pmol/min/mg protein; n=26), and low-affinity (OCTN1) carnitine uptake (K(m) of 412.6+/-191 microM; V(max) of 32.7+/-20.5 pmol/min/mg protein; n=18). Identification of individuals with defective sperm carnitine transport may provide potentially treatable etiologies of male infertility, responsive to L-carnitine supplementation.
Xuan
Wanli
W
Division of Neurology, Department of Pediatrics, The Hospital for Sick Children, Ont., M5G 1X8, Toronto, Canada.
Lamhonwah
Anne-Marie
AM
Librach
Clifford
C
Jarvi
Keith
K
Tein
Ingrid
I
D002331:Carnitine / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins; D008970:Molecular Weight; D027701:Organic Cation Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000074058:Solute Carrier Family 22 Member 5; D013081:Sperm Motility / Q000502:physiology; D013094:Spermatozoa / Q000378:metabolism*; D027981:Symporters; D000099254:Organic Cation Transporter 3
D002331:Carnitine; D002352:Carrier Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D027701:Organic Cation Transport Proteins; D000074058:Solute Carrier Family 22 Member 5; D027981:Symporters; D000099254:Organic Cation Transporter 3; C109807:SLC22A4 protein, human; C492020:SLC22A5 protein, human