The Functional Study Of GDI2 In Photoreceptor Cells

Retinitis pigmentosa(RP)is an inherited retinal disease in which photoreceptors gradually degenerate and die,and retinal pigment epithelial cells become dysfunctional,resulting in night blindness,progressive loss of the visual field,and eventual blindness.At present,the incidence of RP is relatively high,and there is no effective treatment.Available research data have shown that RP can be caused by gene mutations related to the function of photoreceptor cells in the retina.Rhodopsin and some other membrane proteins are important components of photoreceptor cells for phototransduction,and their abnormal transport is an important cause of RP.Recent studies have shown that the Rab GTPase is involved in regulating the transport of proteins in photoreceptor cells,such as Rhodopsin.As one of the key regulators of Rab GTPase activities,GDI2 may be involved in the transport of proteins to photosensitive outer segments.Therefore,it is of great significance to study the role of GDI2 in regulating membrane protein transport in photoreceptor cells to promote our understanding of the mechanism of RP.In this study,the conditional gene knockout technique was used to obtain mice with specific GDI2 gene knockout in the retinal tissue by using the Cre/Loxp recombination system,providing an animal model for the experiment.During the experiment,electroretinogram was used to detect whether the retinal function was affected and to what extent.Immunohistochemistry and confocal microscopy were used to observe the characteristics of the retinal structure,including the morphology of the retina,the changes in the expression and distribution of specific proteins and the relationship between them.The expressions of GDI2,Rhodopsin and other membrane proteins in the retina were qualitatively and quantitatively analyzed by Western blot to determine whether GDI2 was involved in the transport of proteins in the inner membrane of photoreceptors and its role in the transport process.Experimental results showed that,compared with wild-type mice in the control group,when GDI2 conditional knockout mice were at P30,the retina morphology began to change and the outer nuclear layer began to thin.In addition,ERG amplitudes were reduced in knockout mice under the scotopic condition,but there was no significant change in ERG response under the photopic condition,indicating a decrease in the number of rod cells or abnormal function.At the same time,it was found thatGDI2 gene knockout would lead to abnormal distribution of golgi bodies in the outer nucleus layer of the retina of mice and abnormal localization in the outer nucleus layer.At the protein level,by using the quantitative analysis and confocal microscope to evaluate the protein expression level and the distribution of proteins,we found that the rhodopsin level in knockout mice of was markedly increased,and accumulated in outer segments of photoreceptors.In contrast,the expression level and intracellular localization of GC1,GC2,GRK1 or PDE6 did not change.According to the above experimental results,it is concluded that GDI2 is not essential for the transport of rhodopsin and is not necessary for the transport of most membrane proteins.GDI2 is involved in the regulation of rhodopsin protein transport,probably by regulating golgi bodies.GDI2 deficiency will facilitate Rhodopsin transport to the out segment.Excessive Rhodopsin in the outer segment leads to the abnormal function of rod cells,which eventually leads to retinal degeneration.The defective transport of Rhodopsin may be caused by the morphological and functional abnormality of the golgi body caused by the absence of GDI2,and the underlying specific mechanism remains to be further studied.