Rotational dynamics of luteinizing hormone receptors and MHC class I antigens on murine Leydig cells.
We have examined the molecular motions of luteinizing hormone (LH) receptor and the Major Histocompatibility Complex Class I antigen on murine Leydig cells. Using time-resolved phosphorescence anisotropy methods, erythrosin (ErITC)-derivatized ovine luteinizing hormone (oLH) bound to the LH receptor appears rotationally mobile with rotational correlation times of 19.6 +/- 1.3 microseconds, 13.3 +/- 2.4 microseconds, 9.5 +/- 0.7 microseconds and 4.7 +/- 0.5 microseconds at 4 degrees C, 15 degrees C, 25 degrees C and 37 degrees C, respectively. Rotational correlation times for human chorionic gonadotropin (hCG)-occupied LH receptors were similar to those of the ErITC-oLH occupied receptor at each temperature. In addition, both oLH- and hCG-occupied LH receptors were laterally mobile in fluorescence photobleaching recovery experiments with diffusion coefficients at 29 degrees C of (5.8 +/- 0.9) x 10(-10) cm2 s-1 and (2.9 +/- 0.4) x 10(-10) cm2 s-1, respectively. We also measured the rotational correlation time of Class I antigen on murine Leydig cells using ErITC-derivatized 34-12-2S, an anti-Class I monoclonal antibody. Because there was no decay of the anisotropy function at 4 degrees C, 15 degrees C, 25 degrees C or 37 degrees C in the absence of oLH or following preincubation of Leydig cells with 1 nM oLH, it appears that Class I is rotationally immobile on the 1 ms timescale of our experiments. This result is consistent with the presence of Class I antigen in large molecular weight structures and may be the result of Class I self-aggregation. Further, treatment of cells with anti-Class I antibody had no effect on either basal or oLH-stimulated testosterone secretion. Thus, it appears that this anti-Class I antibody is not LH-mimetic on murine Leydig cells.
Philpott
C J
CJ
Department of Physiology, Colorado State University, Fort Collins 80523, USA.
Rahman
N A
NA
Kenny
N
N
Londo
T R
TR
Young
R M
RM
Barisas
B G
BG
Roess
D A
DA
D000818:Animals; D002462:Cell Membrane / Q000502:physiology; D006063:Chorionic Gonadotropin; D004923:Erythrosine; D005454:Fluorescence Polarization; D015395:Histocompatibility Antigens Class I / Q000502:physiology*; D007985:Leydig Cells / Q000502:physiology*; D007986:Luteinizing Hormone; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D011974:Receptors, LH / Q000502:physiology*
D006063:Chorionic Gonadotropin; D015395:Histocompatibility Antigens Class I; D011974:Receptors, LH; D007986:Luteinizing Hormone; D004923:Erythrosine